A top state senator was charged Thursday with extortion and official misconduct in a scandal that has tarnished Wisconsin's reputation for squeaky-clean government.

Senate Majority Leader Chuck Chvala said that he would resign his leadership post once his fellow Democrats selected a new leader, which they are scheduled to do Monday.

He said he will remain in the Senate. "I will fight these allegations because they are not true," he said.

The charges against Chvala accuse him of demanding campaign contributions for himself and other Democrats and threatening to block legislation if lobbyists failed to deliver.

The 20 felony counts include extortion, misconduct in public office and filing false reports with the state Elections Board. The most serious charge, extortion, carries a maximum penalty of 10 years in prison. The combined penalty for all charges is 90 years in prison.

He was the second legislator charged in the yearlong investigation into allegations of illegal campaign activity the state Capitol.

The probe began last year after the Wisconsin State Journal reported that legislative caucus employees were illegally coordinating campaign activities from their state offices using state resources.

Chvala, 47, was elected to the Senate in 1984 and has been Democratic leader since 1995. He ran for governor in 1994, losing to then-Gov. Tommy Thompson, who is now the U.S. health and human services secretary.

Earlier, Democratic Sen. Brian Burke was charged with using his Capitol office to collect campaign contributions in his now-defunct bid for attorney general.

Milwaukee County District Attorney E. Michael McCann, who investigated Senate Democrats, said he expects no other charges against elected officials in his investigation. Dane County District Attorney Brian Blanchard, who is investigating Senate Republicans and the Assembly, declined to comment.