WASHINGTON -- Voters in northern Minnesota may be ready to return a Democrat to Congress next month, a potential setback for Republicans who captured the U.S. House seat for the first time in seven decades in a national GOP wave two years ago.

DFL challenger Rick Nolan, who last served in Congress in 1981, leads freshman Republican Chip Cravaack 50 percent to 43 percent, according to a poll of likely voters in the Eighth Congressional District conducted last week for the Star Tribune.

That's a lead of seven percentage points for an underfunded challenger in a nationally watched race that has drawn more than $4 million in spending by the national parties and outside interest groups. Seven percent of the 1,000 people contacted by the poll remain undecided.

The Cravaack campaign disputed the poll numbers, saying they do not track with other polls in the race. "There is not a single person who would say these numbers are reflective of the state of the race," said Cravaack advisor Ben Golnik, who also took note of Star Tribune poll data showing Cravaack with a seven-point lead among independent voters. "As is always the case in Minnesota, independent voters determine the winner," he said.

Nolan campaign manager Michael Misterek said the poll reflects the momentum Democrats have been seeing on the ground, though he still predicted a close race: "This has been a neck-and-neck race and we believe it will continue to be close going into election day."

The heavy advertising blitz in the Twin Cities and Duluth media markets has put the race on its own trajectory, with Nolan climbing above President Obama's 47 percent level of support in the district, a traditional DFL stronghold that includes the Iron Range.

Cravaack, for his part, polls below the 46 percent level of support for GOP presidential candidate Mitt Romney in the district, which also includes Republican-leaning counties outside the Twin Cities' northern suburbs.

The poll, conducted for the Star Tribune by Pulse Opinion Research, has a margin of sampling error of plus or minus 3 percent. That means Obama and Romney, at 47 to 46 percent, are in a statistical dead heat in the district, compared to statewide polls that show Obama leading comfortably in Minnesota.

The poll also shows that Cravaack, a political novice with less than two years in office, has left constituents with evenly divided views of his performance. Overall, 41 percent view him favorably, while 40 percent say they have an unfavorable impression.

Cravaack's backers describe him as a fresh face who has brought more vigor to the job than Jim Oberstar, a long-time DFL stalwart whom Cravaack edged out in one of the biggest political upsets of the 2010 congressional elections.

"He's newer at the game than some of them, but I think he's done well," said poll respondent Glenice Heineman, who runs a manufacturing business with her husband in Rush City.

Nolan, who is a little less well-known, has a 39 percent favorable rating, with 34 percent viewing him unfavorably.

"He seems like a more down-to-earth kind of guy," said Nolan supporter George Haraden, a shop teacher in Mountain Iron. "He seems to understand people who are working and struggling."

Those reviews come as Democrats and their allies have been hammering Cravaack for his support of a Republican budget plan in Congress that would turn Medicare into a premium-support or voucher system, which Democrats say would weaken the program for future seniors.

"That ain't gonna work," said Lonnie Stockwell, a 59-year-old poll respondent from Grand Rapids who works at Home Depot and who supports Nolan. "I've paid into it. I'm going to need Medicare."

Cravaack has argued that current Medicare spending is unsustainable, and that the senior health insurance system needs to be changed to survive long-term.

That argument resonates with poll respondents like Christie Milam of Chisago City, a 46-year old home-schooling mom. "He has a different view of where he's going to spend the money for Medicare," she said. "It does need to be reformed in some way."

Overall, 43 percent of poll respondents said Nolan would do a better job of protecting Medicare, compared with 39 percent who said Cravaack would.

But on the economy, which emerged as the top issue in the poll, Nolan and Cravaack tied at 43 percent on who would be more effective.

Cravaack is running largely on a jobs platform that would promote mining by easing environmental regulations. As a former union pilot, he has tried to make inroads with union members, a core DFL constituency in the district. "I think there are a lot of closet Republicans in this union up here," said poll respondent Michael Schmitz, a 54-year-old Minntac mine worker in Virginia, on the Iron Range.

"I agree with a lot of what he has to say," Schmitz said, adding that he used to be a staunch Democrat.

Nolan, with support from organized labor but no recent record on economic issues, has been labeled in GOP attack ads as a cookie-cutter liberal from the 1970s, when he represented another congressional district in central Minnesota. He's also been attacked over a troubled record in business and as a former state trade official under the late Gov. Rudy Perpich.

But Nolan has run as a supporter of Obama policies on infrastructure spending, health care, and ending the Bush-era tax cuts for the wealthy. That has won him the support of lifelong Democrats like Jean Wasbotten, an 82-year-old widow in Hermantown, a Duluth suburb. "The economy is coming back," she said. "It's slow, but it's coming back."

On one of the most talked-about issues in the race, the decision of Cravaack's family to move to New Hampshire for his wife's job, 52 percent of poll respondents said it was not at all or not very important, while 42 rated it somewhat or very important. Cravaack says he maintains a significant presence in the district.

Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.