PRAGUE, JUNE 8 -- Czechoslovaks went to the ballot box today in their first free election in four decades, and opinion polls predicted a solid victory for Civic Forum, the party of former dissidents that has steered the country since November's anti-Communist revolution.

The first day of the two-day parliamentary election was orderly but clouded by the growing controversy over a prominent politician who is resisting a government request that he withdraw because of evidence that he was a paid informant of the secret police.

At least 166 candidates from all the major parties have quietly shelved their candidacies, many of them after being linked to the secret police. But the case of Josef Bartoncik, leader of the center-right People's Party, is unusual because it has been so public and appears to involve a political double-cross of no less a figure than the widely esteemed acting president, Vaclav Havel.

The Bartoncik affair also illustrates perhaps the most delicate and morally ambiguous issue of the campaign: the provisional government's attempt to deal fairly with potentially explosive secret police archives.

The controversy provides an unexpectedly turbulent finish to an otherwise placid campaign. At stake are 300 seats in a new federal parliament that will choose a president and rewrite the nation's constitution. Races for positions in the Czech and Slovak republics' legislatures will also be decided.

The polls close at 2 p.m. Saturday and unofficial returns are expected soon afterward. Official results will not be known until Sunday.

Civic Forum's strategists retained the moral capital they gained during the revolution, countering widespread citizen mistrust of political parties by pretending not to be one. Instead, their campaign materials emphasized such popular and respected figures as Foreign Minister Jiri Dienstbier and Finance Minister Vaclav Klaus.

The Forum's trump card was Havel himself. The former playwright, who served time in Communist jails for his dissident views, generally avoided overt endorsement of the Civic Forum. But in public appearances during the frenetic 40-day campaign, his preference was clear.

The Forum's stategists also refrained from direct attacks on the disgraced Communist Party. The exception to that came in the conservative, Catholic republic of Slovakia, when the Civic Forum's Slovak counterpart, Public Against Violence, was losing ground to a new coalition of center-right Christian Democratic parties that painted the Forum as a haven for closet Communists. The Christian Democrats published damaging information from police files about the early Communist Party careers of people who went on to become the country's leading dissidents in the 1960s and '70s.

The Forum and Public Against Violence fought back, and the government set up a commission to evaluate evidence and discreetly screen parliamentary candidates.

The idea was to keep the archives from becoming a political weapon by giving those with compromised pasts a chance to bow out quietly before being exposed, and to keep the new parliament free of those especially vulnerable to blackmail.

The Civic Forum was the first party to agree to have all of its candidates investigated, and at least two dozen subsequently withdrew.

Bartoncik's problems became public earlier this week when he checked into a Prague hospital complaining of chest pains -- one day after a meeting with Havel. At that meeting, Bartoncik reportedly was informed of the evidence detailing his past, and he agreed that he would withdraw his candidacy on health grounds.

Bartoncik went to the hospital but never got around to withdrawing. So Wednesday night the government did it for him, issuing a statement saying that Bartoncik was compromised and would have to withdraw. The statement noted that Bartoncik had broken his promise but did not detail the evidence against him. The accusations against Bartoncik had surfaced three weeks earlier in an Austrian news weekly, and this week the newspaper of the Czechoslovak Agrarian Party published Bartoncik's alleged secret police identification number and code name.

Bartoncik's People's Party has accused the government of abuse of power and attempted blackmail but did not dispute the evidence against Bartoncik.

Tonight, Havel broke his silence and said on national television that Bartoncik had promised to step down, adding that he was ready to produce the government official who had witnessed the meeting.

The most recent opinion polls show Civic Forum likely to get between 30 and 40 percent of the vote, with the Christian Democratic Union coming in second. Support for the Communist Party has been hovering at between 8 and 13 percent.

Civic Forum has said it will enter into a coalition government -- which is thought likely to be necessary -- with any party except the Communists and the extreme right-wing Slovak Nationalist Party.

In addition to drawing up a new constitution, the next government will face the daunting task of retooling Czechoslovkia's economy at a time when its major trading partner and source of energy, the Soviet Union, is floundering.

But many voters seemed willing to temporarily forget those worries and revel in the historic day.

"We have waited for this day for 44 years -- it's a great day," said Alexander Taac in the Slovak capital, Bratislava.

The last free elections in Czechoslovakia were in 1946, when the Communist Party, promising utopia to a country devastated by Nazi occupation and partition, won 38 percent of the vote. Two years later the Communists, taking directions from Moscow, banned most other parties and established one-party rule.Special correspondent Michael Z. Wise in Bratislava contributed to this report.