COLOMBO: As Sri Lanka prepares for its third general election in four years, one theme recurs constantly in newspaper front pages and TV newscasts - the constitution.

The island's left-leaning President Chandrika Kumaratunga and its pro-business Prime Minister Ranil Wickremesinghe - whose parties are due to slug it out in the April 2 election - take regular stabs at one another, often quoting constitution article so-and-so or amendment this-or-that.

It's an uneven battle, because under the 1978 constitution, the island republic adopted a French-style presidential system, with an all-powerful president and a weak prime minister.

"Under the current constitution, the prime minister is put in office, but not in power," Eric Fernando, director-general of the presidency's policy research unit, said.

As long as both are from the same party, everything runs smoothly. Kumaratunga won a second six-year mandate in 1999, but Wickremesinghe's United National Party (UNP) defeated her Sri Lanka Freedom Party (SLFP) in the 2001 general election. Since then, they have lived in an uneasy cohabitation.

Wickremesinghe had run on a platform of economic reform and peace with the Liberation Tigers of Tamil Eelam (LTTE). His government signed a ceasefire with the rebels in February 2002.

When Wickremesinghe wanted to complete the truce with a political deal involving devolution of central power, the staunchly nationalistic Kumaratunga put her foot down.

In November, while Wickremesinghe was in the United States explaining the peace process to President George W. Bush, she seized the ministries of defence, interior and the media.

Her move turned a simmering feud into a gloves-off battle between the two and deadlocked the peace process with the Tigers. A week ago, Kumaratunga ended the standoff by calling elections and sacked 39 of Wickremesinghe's junior ministers to prevent their access to government resources such as state vehicles during the election campaign.

"Never has the president's office been abused to such an extent," Wickremesinghe spokesman G.L. Peiris said. Peiris, a constitutional expert, knows the rules of the game.

In the stalemate that has frozen the peace process since November, Kumaratunga is the undisputed queen of the board, while Wickremesinghe has the limited movement of a rook. If she wanted to sack him too, she could do it today.

A DOSE OF UNCLE'S MEDICINE: Wickremesinghe has huge popular support though because the truce ended a two-decade-old war that has killed more than 64,000 people.