"To set Illinois on a course for reform and honest government, I will be a candidate for the United States Senate," Kirk said.
The 48-year-old North Shore congressman chose to make the announcement outside the home where he lived as a teenager in Kenilworth, reportedly the wealthiest suburb in all of Illinois. Still, the Republican said he was not worried about being labeled the candidate for the privileged.
"This is where I grew up, and this is who I am," said Kirk.
The five-term congressman, who will have to give up his seat in the House, says he's running against the Democrat establishment -- Blagojevich, Madigan, Daley and others-- that has controlled virtually all of Illinois politics since 2002.
Republican leaders have agreed to do what they can to make sure Kirk runs unopposed in the February primary.
"Clearly, this is a very good opportunity for Republicans. People are very turned off by the Democratic leadership," said Ill. Republican Chairman Andy McKenna.
On the Democrat side, Illinois Treasurer Alexi Giannoulias says he will declare his candidacy within the next week. He was asked what he thought of Kirk's choice to announce in wealthy Kenilworth.
"You're talking about someone who voted for George Bush's tax cuts for the wealthy and voted against the minimum wage," Giannoulias said.
The new Senate candidate Kirk was heckled during his outdoor announcement.
"Those are the left-wing guys, I think. We'll have the right next," he responded.
The demonstrators disagreed with Kirk's positions and votes in Congress on health care and immigration reform.
"We think the Latino and other immigrant communities simply will not vote for someone who does not have a solution for a broken immigration system," said immigration reform activist Ahmed Rehab.
Kirk is a Naval Reserve intelligence officer who has served tours in both Iraq and Afghanistan. He calls himself strong on defense, fiscally conservative, but moderate on social issues.
"Together, we will restore pride in Illinois, and we will bring this kind of reform and honestly that state government it deserves," he said.
Also Monday, Congressman Kirk said the file in his divorce earlier this year had been opened and reviewed by party officials. His ex-wife, Kimberly Vertolli, appeared briefly at a post-announcement news conference Monday to say that she supported Kirk's candidacy.
The personal information came up only because of what happened to Republican Senate candidate Jack Ryan in 2004 when personal issues entered his campaign. Barack Obama ended up winning his seat.