Democratic Senator Kohl says will retire

U.S. Supreme Court nominee Sonia Sotomayor (R) talks to Senator Herb Kohl (D-WI) during their meeting on Capitol Hill in Washington in this June 3, 2009 file photo.

MILWAUKEE, Wisconsin (Reuters) - Four-term Senator Herb Kohl said on Friday he will not seek re-election next year, joining five other Democrats who plan to retire and making it tougher for their party to retain the chamber.

Kohl, 76, of Wisconsin, was re-elected in 2006 with 67 percent of the vote. He had been listed by the Cook Political Report, a prominent nonpartisan newsletter, as a solid favorite to win another six-year term in the November 2012 elections.

"I've always believed it is better to leave a job a little too early than a little too late," Kohl said at a news conference at his Milwaukee office. "The interest and energy I had for this job will find a new home."

Former Senator Russ Feingold, who was defeated in 2010, and Representatives Ron Kind and Tammy Baldwin appear to be the leading potential Democratic candidates for Kohl's seat.

An online poll by the Milwaukee Journal Sentinel newspaper showed Feingold and Republican Representative Paul Ryan of Wisconsin as favorites to succeed Kohl.

Jennifer Duffy, who tracks Senate races for the Cook report, said she expects Feingold to consider running -- or at least be urged to do so.

"His prospects would be 50-50 at best" to win, Duffy said. "It's hard to lose a Senate seat and come back two years later.

"I think the jury is out on what the political environment in Wisconsin will look like 18 months from now. Both parties are likely to be energized," said Duffy, who with Kohl's announcement moved his seat from "solid Democrat" to "tossup."

NARROW MAJORITY AT RISK

Democrats control the Senate 53-47. But they face difficulties holding their majority in 2012, when 23 Democratic seats are up for grabs, as opposed to 10 seats now controlled by Republicans.

Seven other senators have announced their retirements: Democrats Daniel Akaka of Hawaii, Jim Webb of Virginia, Kent Conrad of North Dakota, and Jeff Bingaman of New Mexico; independent Joe Lieberman of Connecticut who caucuses with Democrats; Republicans Kay Bailey Hutchison of Texas and Jon Kyl of Arizona.

Kohl, who made a fortune in his family's department store business and bought the Milwaukee Bucks professional basketball team in 1985, has had a mostly liberal voting record during his Senate career.

Kohl holds a seat on the powerful Senate Appropriations Committee and serves on banking and judiciary panels.

He has supported government mandates for more fuel-efficient vehicles, capping greenhouse gas emissions blamed for global warming and an expansion of healthcare for poor children.

He also backed legislation calling for a U.S. troop withdrawal from Iraq in 2008 and immigration reform giving certain illegals in the United States a path to citizenship.

(Additional reporting by Thomas Ferraro and Richard Cowan in Washington; Editing by Xavier Briand)