It worked in Massachusetts, so Illinois Republicans are looking for a repeat.

"This is not Obama's seat, it's the people's seat," Rep. Mark Steven Kirk, the Republican candidate running for Illinois' Senate seat vacated by the president, declares at campaign stops.

Eager to tap the voter angst and stump lines that propelled Sen. Scott Brown to unexpected victory in another Democrat-dominated state, Massachusetts, Mr. Kirk has made it clear that even though the president remains popular in his home state, his policies aren't.

And with just 38 percent of all Illinois voters giving Mr. Obama good or excellent ratings for his handling of health care reform, the five-term lawmaker is actually putting the Democratic stronghold in play.

"For the first time in a long time, the Republicans have a good chance of winning this Senate seat," said Paul Green, a professor of policy studies at Roosevelt University in Chicago.

Republican Party leaders in the state are making no secret that they'll target Mr. Obama as the consummate Washington insider, and the latest polls indicate some traction. A Rasmussen poll last week showed the race statistically tied, with Mr. Kirk trailing Democrat Alexi Giannoulias, the treasurer of Illinois and a basketball-playing friend of Mr. Obama's, by just three points, well within the survey's margin of error.

"President Obama's still very popular here, and he will always be popular here, but he hasn't shown any coattails," said Pat Brady, the state's Republican Party chairman.

"Anyone who's running against any of our Republicans in congressional or Senate campaigns, we're going to tie them directly to President Obama's policies, which are not popular here."

But some analysts say the GOP is walking a dangerous path in a blue state and suggest not overplaying the hand.

Mr. Green said Mr. Kirk could take an anti-Washington stance, attack House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid, "but I'd stay away from Obama."

"He has to be careful, only because Kirk's success has been he's been able to straddle, to get a lot of people who vote Democratic to vote for Kirk," he said. "The Democratic Party here is in a whole bunch of trouble. You could spend all day doing that."

The woes of the Democratic Party, said DePaul University political analyst Michael Mezey, should keep the Republican from focusing his campaign on the president.

"That's probably the one mistake Mr. Kirk could make. I think Kirk would be silly to do this when he is running against a candidate who can be attacked on his own and has numerous weaknesses," he said.

Illinois Democrats have been mired in political scandals. In January 2009, the state legislature impeached and ousted Democrat Rod R. Blagojevich as governor. His trial on charges of racketeering, fraud, lying to investigators and trying to sell Mr. Obama's former U.S. Senate seat to the highest bidder is set to begin in June and could run right up to the November election.

Mr. Obama's replacement in the Senate, Roland W. Burris, also made headlines when reports emerged that he had contacts with Mr. Blagojevich's brother before being appointed. The Senate Ethics Committee admonished him in November 2009; Mr. Burris is not seeking election to the seat.

In addition, Scott Cohen, a pawnbroker-turned-politician who won the Democratic nomination to run for lieutenant governor, became embroiled in a scandal over charges that he beat his girlfriend in 2005. Just a week after winning the nomination in February, he dropped out of the race.

Mr. Giannoulias, 33, has plenty of his own problems. He has been under scrutiny as state treasurer for his handling as of a college savings program that lost $150 million. His family's bank, Broadway Bank, where he worked as a lending officer before entering politics, is on the verge of takeover by the Federal Deposit Insurance Corporation. The bank made hundreds of millions of dollars in bad loans and shortly before the mortgage crisis, the Giannoulias family withdrew $70 million from the bank in 2007 and 2008, according to news reports.

Mr. Giannoulias also made millions of dollars in loans to Tony Rezko, a political fundraiser for Mr. Blagojevich who is awaiting sentencing on convictions of fraud and money laundering. He also made loans to Michael "Jaws" Giorango, a convicted prostitution-ring operator.

The National Republican Senatorial Committee has gotten in on the act, issuing a Web video last month that mocked Mr. Kirk's opponent, asking at the end: "Is this change we can believe in?"

Mr. Obama carried Illinois over Sen. John McCain by a whopping 25 percentage points, 62 percent to 37 percent, in 2008. Fifty-six percent of voters in the state now approve of the job he is doing as president, the latest poll found.

What's more, Illinois voters, by a 52 percent to 39 percent margin, oppose the massive health care reform bill in its current form, preferring Congress pass smaller bills that address individual problems in a step-by-step approach.