MADISON — Sounding the same campaign themes that succeeded in the past two hotly contested Supreme Court elections, a Jefferson County judge announced his candidacy today.

Judge Randy Koschnick, who will challenge Wisconsin Supreme Court Chief Justice Shirley Abrahamson, said he was a judicial conservative and that his opponent was an activist who legislates from the bench.

The two most recently elected justices, Annette Ziegler and Michael Gableman, used similar themes in their races, which were marked by vicious attack ads and millions of dollars in spending by outside groups.

Koschnick’s campaign already has a partisan feel. His consultant is Darrin Schmitz, a Republican who ran Gableman’s campaign for the court earlier this year.

Koschnick’s spokesman is Todd Allbaugh, a Republican candidate for the state Assembly this year who lost in the September primary. He also formerly worked for Republican state Sen. Dale Schultz of Richland Center.

Abrahamson, a 32-year veteran of the court, has said in recent speeches that the independence of the judiciary is put in jeopardy with high-cost, partisan judicial races.

“Wisconsin judges have both an institutional and personal interest in the election of judges and the tenor of campaigns,” she said in her annual state of the judiciary speech delivered last week. “We must ensure that judicial campaigns are worthy of the electorate.”

Koschnick said he agreed with Abrahamson that judicial races should be publicly financed. He also offered a clean campaign pledge that includes a promise to repudiate false accusations made by third-party groups during the campaign.

Abrahamson was in a meeting with other justices and did not immediately return messages left for her at the court or with her campaign office.

Koschnick’s announcement sets the stage for what could be another expensive contest for the Supreme Court. About $6 million has been spent in each of the past two Supreme Court elections, with much of it coming from outside groups.

Wisconsin Manufacturers and Commerce, the state’s largest business group, spent $4 million combined on behalf of successful candidates Ziegler and Gableman, according to an estimate by the government watchdog group Wisconsin Democracy Campaign.

WMC spokesman Jim Pugh said he didn’t know yet how big a role the group would play in the upcoming race.

“Our board hasn’t considered it,” he said. “We communicate the messages that we think are appropriate about the issues that affect Wisconsin. That’s what we’ve done in the past and what we’ll do in the future. We’re going to leave it at that.”

Abrahamson, 74, was appointed to the court in 1976 and has been re-elected ever since. She has served as chief justice since 1996.

Koschnick was elected judge in 1999 and previously worked 14 years as a public defender in La Crosse and Jefferson counties.

Koschnick said that while his record as a public defender may be used against him in the campaign, as it was against Butler, he believes that would be a losing strategy.

The officially nonpartisan election is April 7. There are no other declared candidates.

In the past race, the court’s ideological balance was at stake. But with the Gableman win, conservatives are generally perceived to have a 4-3 majority on the court.

An ethics charge from this year’s race in which Gableman defeated Justice Louis Butler remains unresolved.

The Wisconsin Judicial Commission filed a complaint against Gableman in October, saying he committed misconduct when he ran a television ad that falsely suggested Butler helped free a child molester.

A three-judge panel will hear the charge and recommend discipline to Gableman’s colleagues on the Supreme Court, which could range from a reprimand to removal from the bench.