Senator Russ Feingold - the maverick Democrat who championed campaign finance reform - is struggling to hang onto his Wisconsin senate seat amid an onslaught of attacks ads aimed at stirring up voter frustration with Washington.

In any other election year, the three-term incumbent from this Democratic-leaning midwestern state should have easily beat opponent Ron Johnson, a wealthy businessman with no previous political experience and little in the way of specific policy proposals.

But voters are frustrated with the slow pace of the economic recovery and Democrats -- who control Congress and the White House -- are bearing much of the blame.

Further complicating matters is a recent Supreme Court decision to overturn the campaign finance law Feingold co-authored and allow corporations to essentially spend as much as they want on political advertising.

While Feingold has stuck to his principles and told outside groups to stay away -- including the Democratic Party's Senatorial Campaign Committee -- Johnson has not.

The plastics manufacturer has spent millions of his own money on the race and outside groups have spent more than two million dollars on ads either supporting Johnson or attacking Feingold, according to the Sunlight Foundation.

One cartoonish ad paid for by a group called Speech Now paints Feingold as a double-talking Washington insider who voted for "government run health care, huge tax increases and record debt."

"Ranked as the most liberal senator, he even attacked our first amendment right to free speech, while here in Wisconsin: more economic pain," a narrator says over scenes of shuttered stores and a bobbleheaded Feingold being carried on the shoulders of House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid.

Other ads, paid for by the American Action Network, declare "Russ Feingold and our money -- what a mess" and "can we really afford him anymore?"

Feingold is hoping that Johnson's ad blitz will backfire.

"He's trying to buy this election but we're not going to let him do it," Feingold told an enthusiastic group of a few hundred supports who huddled under umbrellas at a Milwaukee early-voting rally Saturday.

"We will be outspent, but we will never be out-organized. This seat will not be bought. It has to be earned. And we'll earn it right now before the rain gets worse by going to vote!"

Key to a Feingold win is closing the "enthusiasm gap" and getting Democrats out to vote, said Charles Franklin, a co-founder of who teaches political science at the University of Wisconsin at Madison.

"Motivating the Democratic base and maybe some moderates to turn out is essential to Feingold pulling this back," Franklin said in an interview.

"The most important thing is to get people thinking about voting and to get volunteers."

President Barack Obama drew 26,000 people to a rally in the state capital and college town of Madison in September and Michelle Obama has also been to Wisconsin to rally support for Feingold.

There was plenty of enthusiasm at the rally Saturday, where Feingold got the biggest cheers of all the Democratic candidates and well-wishers hugged him and shouted "God bless you, senator."

Teacher Laurie Mozlin, 59, has been making phone calls on behalf of the Feingold campaign and talking to everyone she knows about why they should reelect him.

"I hope Feingold will pull it off," said Mozlin, who drove an hour from her home in Kenosha to attend the rally.

"He really is the most independent voice in probably both houses of Congress. He votes what he believes."

While Feingold has maintained high job approval with voters, he was trailing Johnson by seven to 11 points for much of September and early October in polls of likely voters.

But a poll released last week showed that Johnson's lead had narrowed to just two points, well within the five point margin of error.

Feingold told reporters Saturday that he's feeling good about his chances and has a history of winning close races.

"I've done these kinds of rallies all across the state because I really believe that as may people as possible should be involved in making this decision and that's how we're going to win," he said.