Jakarta – Senior party executives and campaign managers for the top three presidential hopefuls are wrestling with coalition building for the expected Sept 20 run-off election.

With all the horse trading going on, analysts say front runner Susilo Bambang Yudhoyono faces an even tougher fight in the second round.

With just over half of the vote counted, Mr Bambang is leading with 34 per cent. President Megawati Sukarnoputri is second with 26 per cent, followed by former general Wiranto with 22 per cent.

But in the minds of many, Mr Bambang – despite the momentum of a first-round victory – could be facing a combined offensive from the country's strongest political organisations.

He will face an uphill battle, said Mr Entjeng Sobirin of the Institute for Social and Economic Research (LP3ES).

"He has to develop a new strategy because he simply doesn't have the political machinery to compete," he added.

But Mr Sofyan Djalil of the Democratic Party ruled out the possibility of Mr Bambang building a 'grand coalition', saying any alliance 'would not be comprised of many big elements'.

He added that Mr Bambang's government, which will be built on a small coalition, will be ready to face strong opposition from the House of Representatives.

Golkar and Ms Megawati's Indonesian Democratic Party of Struggle (PDI-P) are the two largest factions in the House with 129 and 109 seats respectively.

Golkar executive Bomer Pasaribu said that in the event of a Wiranto defeat, a coalition with the PDI-P was one of the scenarios being looked at. "But of course, we would have to look at how Gus Dur [Mr Abdurrahman Wahid] stands on the issue of endorsing Megawati," he added.

The former president still wields considerable influence among the millions in Islamic organisation Nahdlatul Ulama, especially in East Java.

Political analysts Syamsuddin Haris and Daniel Sparringa said Mr Bambang would be facing a major coalition of Golkar and PDI-P heavyweights.

And apart from Golkar chairman Akbar Tandjung, presidential candidate Amien Rais is likely to sway towards Ms Megawati as well, said Mr Syamsuddin. "Negotiations with Megawati are likely to be more amiable than with Bambang, who from the start has tended to ward off other parties," he added.

But despite the politicking of the party elite, voters in the end could still buck the trend of established political deals, said analyst Daniel Sparringa.

As the legislative and presidential elections have shown, Indonesian voters are gradually moving away from traditional ethnic lines, rendering preconceived political allegiances obsolete, he pointed out.