The candidate who gets the most votes overall and leads the presidency could determine whether Bosnia splits apart into separate ethnic republics or hangs on as one nation.
It was far too early to predict the winner - only a fraction of the 109 electoral districts were reporting partial results for the presidency by yesterday evening.
Robert Frowick, the American diplomat overseeing the elections, said final results for the presidency would not come before today. Results in other contests in the two halves of Bosnia are expected even later.
Voters in Saturday's first postwar national elections could choose only one of the 16 candidates for the presidency. The top Muslim, Croat and Serb candidates will comprise the presidency; the top choice overall will be chair for two years.
Preliminary results released yesterday show Bosnia's President Alija Izetbegovic as the top choice of Muslims, who dominate Bosnia's Croat-Muslim federation. Ahead in the Serb half of Bosnia was nationalist Momcilo Krajisnik.
If Izetbegovic wins, he is expected to press for a unified Bosnia, while Krajisnik favors having Serb areas of Bosnia join Serbia.
Most Bosnian Croats were voting for the main Croat candidate, Kresimir Zubak. With Croats outnumbered by Serbs and Muslims, their candidate was sure to come in third.
Though presidency decisions are supposed to be mutual, the chair will be considered first among equals and therefore have a greater voice than his other two colleagues.
The chief election monitor for the Organization for Security and Cooperation in Europe, which staged the elections, said yesterday that Bosnia's future was on the line.
"Whether the election leads to integration or disintegration will only become clear as immediate events unfold," Eduard Van Thijn said in a report on the elections.
There were an estimated 1.1 million eligible voters in the Serb republic and about 1.8 million eligible voters in the Muslim-Croat federation. Although Muslim voters outnumbered the others, it was not certain whether Izetbegovic, the current president, would prevail.
Haris Silajdzic, his former premier, was expected to siphon off some Muslim votes, and organizational problems prevented an unknown number of Muslims from voting near towns they fled during the war.
The Serb candidate, Krajisnik, was more sure of collecting most Serb votes.
That would result in a scenario dismal both to the Muslims, who fought the Serbs for nearly four years, and the international community, which viewed these elections as the first step to Bosnian unity.
The only results available yesterday from 21 federation districts showed Izetbegovic with about 81 percent of the votes in Muslim regions. Silajdzic had about 15 percent.
Zubak, candidate of the main nationalist Croat party, had about 84 percent among Croats in the federation.
In the 17 districts of the Serb region, Krajisnik was ahead with about 78 percent. Mladen Ivanic, a relative moderate supported by Serbian President Slobodan Milosevic, had 20 percent.
The chance of a Serb chairmanship was strengthened with news yesterday that far fewer Muslims crossed former front lines to vote in Serb lands than previously thought.
U.N. spokesperson Alexander Ivanko said only 13,500 Muslims crossed over Serb lines Saturday to vote in or near their prewar hometowns. No more than about 1,200 Serbs went into territory controlled by Muslims and Croats to vote.
These figures, which disappointed international officials, support the contention that after years of ethnic purges in Bosnia, all sides accept the reality of a nation split in two.