CAIRO (Reuters) - It's harvest time in Egypt but the secular opposition is reaping scant benefit from the Muslim Brotherhood's difficulties in government, two years after an Arab Spring uprising swept away President Hosni Mubarak.

 Many Egyptians are looking to the army, or to more radical Salafi Muslim groups, rather than to liberal or leftist parties as Islamist President Mohamed Mursi and his cabinet struggle to revive a sick economy, restore security and build institutions.

 Perhaps the greatest threat to Egypt's faltering transition to democracy may come not from what the Brotherhood's critics regard as its attempts to grab as many powers as possible, but from the inability of a weak and fragmented secular opposition to offer a coherent alternative.

 "I recognize that the opposition has not lived up to the expectation of the people," said Amr Moussa, 76, a former Arab League secretary-general, who is one of the leaders of the opposition National Salvation Front (NSF).

 "But I also recognize that there are lots of possibilities for the opposition to rise to the challenge, especially as the government is not really offering much," the conservative told Reuters in an interview.

Six secular parties and a cluster of democracy activists and intellectuals are loosely allied in the Front, created last November to resist a decree issued by Mursi under which he temporarily took sweeping powers to push through an Islamist-tinged constitution.

 Like the battered vehicles on Egypt's roads, the NSF often seems held together by desperation alone. "What keeps us together is the dire situation of Egypt," said Moussa, a foreign minister under Mubarak for 10 years.

 Mohamed ElBaradei, leader of the liberal Constitution party, said the Front "doesn't really have the luxury right now to say 'this is the left, and this is the center-left or center-right' because what we are opposing is... almost a fascist system".

 He sees the NSF as representing a silent majority of 60 to 70 percent of Egyptians who reject Brotherhood rule and are in "a national state of depression".

 "BATTLE OF THE EGOS"

 Yet the opposition alliance is hobbled by what one NSF aide calls a "battle of the egos" among its leaders, and its component parties agree on few policies.

 Should the opposition engage and compromise with Mursi for the sake of national unity or boycott and try to weaken him to make it harder for the Brotherhood to control the country?

Should they participate in parliamentary elections that many believe will be skewed towards the Brotherhood, as they say all post-revolution votes have been, or stay away at the risk of being marginalized and looking like bad losers?

 And should they back a proposed loan from the International Monetary Fund as essential to pull the economy out of crisis despite the tough terms that would be attached, or oppose it on grounds of national sovereignty and social justice - or just sit on the fence?

 Each time it looks as if the Front is about to break up over one of these issues, the Brotherhood makes another move that reunites the opposition in shared indignation.

 The latest was a clumsy attempt in April to purge the judiciary, which Islamists believe is riddled with corrupt former Mubarak loyalists bent on obstructing elections and laws put forward by elected bodies that the Brotherhood dominates.

 By trying to force more than 3,000 judges into retirement at a stroke, the Brotherhood galvanized the judiciary, the NSF, the Salafis and most of the media against itself, prompting Mursi to beat a tactical retreat and seek a compromise.

Political analysts say the president could pick the secular opposition apart if only he accepted some of its demands to appoint a national unity government, replace a widely reviled prosecutor general and pass a more even-handed election law.

"That would pose a real dilemma for the opposition. But mutual suspicion and the Brotherhood's feeling of being under siege are so strong that I don't expect Mursi will do that," a senior European diplomat said.

BETRAYED

Many opposition activists feel they gave Mursi decisive help to win the presidency by backing him in a run-off against former Mubarak Prime Minister Ahmed Shafik last June, only to be shut out of influence by the Brotherhood.

They feel betrayed on issues such as the constitution, the rights of women and religious minorities, judicial independence, and laws regulating elections, demonstrations and non-government organizations.

"We were betrayed by the Muslim Brotherhood, we were cheated by the Muslim Brotherhood. Now they make the same propaganda against us as the old regime did," said Khaled Dawoud, a spokesman for the NSF and ElBaradei's Constitution Party.

Aside from the NSF, the opposition also features a range of Islamist parties of different shades, including two ultra-conservative Salafi groups, as well as rebranded survivors of Mubarak's outlawed former National Democratic Party (NDP).

The Salafi Nour Party appears to be the fastest growing, although its claim to 800,000 members - more than the entire membership of all political parties in Britain or France - sounds optimistic. Nour led an alliance of Islamic purists that won 27.3 percent of the vote in 2011-12 parliamentary elections and has the second largest bloc of lawmakers.

Nader Bakkar, 29, the party's spokesman who has an MBA degree from Alexandria University, says Egyptians are flocking to Nour because, while it has strict Islamic principles, it does not seek to monopolies power or behave like a closed family.

It is also untainted by the burdens of trying to make government work in a chaotic post-revolutionary environment.

Like the Brotherhood, Nour activists run social and medical services for the poor, distributing free or cheap food. That could pay off at election time in a nation where 40 percent of the population lives on less than $2 a day.

But unlike the Brotherhood's Freedom and Justice Party, which propelled Mursi to power, Nour supports a national unity government that would include liberal opposition figures.

The party has its headquarters in a refurbished Nile-side apartment that could be home to an advertising agency but for the Koranic chanting coming from a TV screen on a wall in the soft pink spotlit reception area.

"The most likely probability is that we will run in the elections alone. It is almost decided that we will not ally with the Freedom and Justice Party," Bakkar said in an interview.

He said Nour wanted to avoid a dangerous polarization on Egyptian streets into Islamists and non-Islamists, and left the door slightly ajar to a pact with some secular parties, although such a marriage of convenience looks improbable.

 While the Nour party eschews strict public enforcement of Islamic behavior as contrary to Egyptian tradition, Bakkar drew the line at wishing Coptic Christians a happy Easter. The Copts, who comprise up to 15 percent of the 84 million population, celebrate the most important festival of the Christian calendar on May 5 this year.

 AMBIGUITY

 The NSF's leaders meet weekly on Wednesdays to try to thrash out their many differences and take joint positions that are sometimes a tortured lowest common denominator.

 On April 18, the Front said in a statement it was getting ready to take part in parliamentary elections while pursuing "the struggle" to create the right atmosphere for a free and fair vote. This ambiguity rapidly backfired on its authors.

 The reality, according to two officials in the NSF who asked to remain anonymous, is that at least two of its parties, the Social Democrats and the veteran nationalist Wafd, are likely to contest the polls, even if the others decide to boycott them.

 Leftist firebrand Hamdeen Sabahi, 58, head of the Popular Current party, told Reuters that if Mursi met the conditions for a fair poll, including the replacement of Prime Minister Hisham Kandil, the Salvation Front would run one joint list.

 While most other NSF groups regard the long-delayed IMF loan as essential to revive the economy, Sabahi said Egypt should reject it because the conditions would further impoverish the poor and could provoke a revolution of the hungry.

Sabahi said the NSF's weakness was exposed by those Egyptians who want a return of the military, which ruled directly through the Supreme Council of the Armed Forces between Mubarak's fall and Mursi's election last year.

"The rise of calls for the Egyptian army (to take power) reflects the fact that there is no hope in the Brotherhood on the one hand, and no trust in the Salvation Front to save us from the Brotherhood on the other," he said.

Ahmed Fawzy, general secretary of the rival Social Democratic Party, admitted his group is divided about whether to run in the elections expected to be held later this year, but said each movement would stand on its own.

Interviewed in the party's drab office in central Cairo, the 41-year-old lawyer said the Social Democrats had 10,000 members, and were among the few groups to have struck roots in southern Upper Egypt since the revolution that began on Jan. 25, 2011.

Nevertheless, it was tough going, Fawzy said. "This is a community that was banned from organizing for about 60 years when there were no real parties, trade unions or NGOs," he said.

"We now have our infant party born after Jan. 25 that has since then been in dispute either with the Military Council or the Muslim Brotherhood and is trying to build itself in tough economic and social circumstances, and Egyptians are not yet used to organized group work."

REVOLUTIONARIES

Sabahi, a former student leader who spent years in jail under Mubarak and earlier, was third in last year's presidential election. During the campaign, he branded Moussa "feloul", a pejorative term for a "remnant" of the old regime.

Moussa in turn regards Sabahi as a "Nasserite crazy", according to sources in the NSF, because of his statist economic views inspired by President Gamal Abdel Nasser who overthrew Egypt's monarchy in 1952 and nationalized swathes of industry.

But Dawoud, the NSF spokesman, says the Front's ideological diversity and personal tensions mask a common purpose.

"We disagree about economic policy, we disagree about the IMF, we may disagree about how to deal with Mursi, but we share the same purpose that we want to defend the democratic, modern, civil nature of the Egyptian state," he said.

The main divide in the NSF, Dawoud said, is between those who see it as a revolutionary movement and those who see it as a political coalition, adding that in his view, it is obviously a political umbrella and not a group of revolutionaries.

One proponent of the revolutionary line is novelist Alaa Al Aswany, author of "The Yacoubian Building", a satire of corruption in the Mubarak era, who was prominent in the Tahrir Square protests that toppled the former ruler.

"What is going on now is not so much a political conflict between the government and the opposition as popular resistance against a group that reached power via elections, yet is desperately carrying on with plans to get hold of the state," Aswany wrote in his column in opposition daily Al-Masry Al-Youm.

Rejecting any compromise with Mursi, Aswany called for the president and his interior minister to be put on trial over the alleged killing and torture of opposition activists.

Such talk infuriates politicians in the NSF who are trying to position themselves as a constructive opposition and believe the way forward is through the ballot box, not the street.

CAIRO-CENTRIC

Few secular opposition parties appear to have much of an organization outside Cairo and a handful of other cities, although Sabahi's Popular Current has built support networks among workers and students.

The Wafd has historic roots older than the Brotherhood's but is seen by younger Egyptians as a tame Mubarak-made opposition that never challenged him in nearly 30 years in power.

The state newspaper Al-Ahram reported that pupils at one school in the coastal city of Alexandria were last month given the exam essay topic: "What is your view of the alliance of losers and thieves who are counting on a corrupt mass media to spoil the efforts of President Mohamed Mursi?"

The subject betrayed the examiners' political slant but it also reflected a broad disenchantment that the opposition has failed to offer a credible alternative to Brotherhood rule.

"I don't trust the Brotherhood, but I'm even angrier at the opposition for not putting forward any vision for Egypt," said Randa Hamlawi, a Cairo office worker