MADISON (WKOW) -- Former Wisconsin Governor Tommy Thompson made it official Thursday evening: he's running for Herb Kohl's vacating U.S. Senate seat.
It has been 13 years since Thompson last appeared on a ballot, now he's running against at least three other Republicans for the spot.
Thompson comes into the race as the frontrunner, but his opponents say he's not conservative enough.
To a crowd of 200 at a Waukesha manufacturing company, former governor and U.S. Cabinet Secretary Tommy Thompson announced: he's back.
Thompson said, "Our country's in trouble. I want to send someone to Washington like myself, who knows how to get things done and has been successful."
Thompson has been accused of being too moderate, and was criticized about his view on the president's health care reforms: he initially supported parts of it, and now says he would vote to repeal it.
Thompson defended himself as a conservative, saying he could get Tea Party votes, "I started the conservative movement when I was governor. I cut taxes 91 times; I created jobs with help of the business community."
Democrats criticize Thompson's involvement in numerous boards and corporations.
Mike Tate, Democratic Party of Wisconsin chair, said, "He owes the people of Wisconsin answers. He should tell them what corporations he works for, and who he's been trying to influence."
Thompson said, "They always have to criticize... what did they expect me to do, be a hermit?"
With this announcement, Thompson joins a crowded Republican field in the race for U.S. Senate. Former Congressman Mark Neumann says he's more conservative than Thompson.
Neumann said, "The most conservative person in the race is really myself and I think a lot of people see that. It's really about balancing the budget and ending ObamaCare, with conservative values all the way through."
Neumann added in a statement, "I'm the only candidate who has a detailed plan to cut trillions in government spending. I opposed ObamaCare from day one, collecting over 25,000 petitions opposing it last year. I'm the only candidate with a 25-year track record in business, creating hundreds of private sector jobs for Wisconsin. I look forward to a debate on the issues as the campaign unfolds."
Also in the race, Republican State Senator Frank Lasee of DePere and Assembly Majority Leader Jeff Fitzgerald, who released a statement saying, "I welcome Tommy to the race. I expect in the coming months we will engage in a substantive conversation about our visions to move Wisconsin forward.... I look forward to sharing my conservative record of balancing a $3.6 billion budget deficit without raising taxes, implementing tort reform legislation and enacting comprehensive election reform... I believe my record demonstrates I am the person who can turn things around in the nation's capital, and I look forward to debate with Tommy and others seeking our party's nomination."
The only Democrat in the race is Congresswoman Tammy Baldwin.
The Republican primary for U.S. Senate is in August.
The seat has been in Democrat hands since 1957.