Democratic U.S. Sen. Amy Klobuchar has opened up a 29 percentage point lead in Minnesota as she prepares to face Republican challenger Kurt Bills, who remains unknown to many voters, according a Star Tribune Minnesota Poll.

Klobuchar captured support from 57 percent of the electorate, with Bills drawing 28 percent. Another 7 percent said they would vote for someone else, while 8 percent remain undecided in the U.S. Senate race.

The poll shows the first-term senator with a solid advantage in all areas of the state, outpacing Bills by more than 40 percentage points in the Democratic urban areas that include Minneapolis, St. Paul and Duluth. Klobuchar's weakest numbers come in southwestern Minnesota, where 46 percent say they would vote for her, compared to 26 percent who favor Bills and 19 percent who are undecided.

Not surprisingly, Klobuchar has a substantial gender gap in her favor, with 62 percent of women saying they plan to vote for her. But more than half of male voters also support Klobuchar, with 34 percent supporting Bills.

Nearly all DFLers -- 93 percent -- say they support Klobuchar, while Bills draws 66 percent of Republicans. Independents, whose support can prove critical, tilt heavily toward Klobuchar, with 49 percent saying they'll support her compared to 27 percent who want Bills. She also wins half of the voters in the metro suburbs and the Rochester area, where Bills picked up support from about a third of voters and Republican Mitt Romney had leads compared to President Obama.

Ticket splitters may be part of Klobuchar's advantage.

Cal Barnett, a Republican from Marshall, plans to vote for GOP presidential candidate Mitt Romney, but in the Senate race he said he plans to mark the box for Klobuchar.

"She has probably been more effective than many people that go to Congress because she has been aggressive and probably has represented the state well," he said.

Part of the hurdle for Bills, a freshman House representative in his first statewide run, has been to establish the name recognition and funding needed for a costly U.S. Senate race. Bills rode a wave of Ron Paul supporters to capture his party's endorsement, but since then has suffered from a low profile among the electorate.

For some Minnesotans, though, just the fact that Bills is a Republican is enough.

Allen Tuff, an Apple Valley Republican, said he does not know much about Bills, but plans to vote for him. Tuff's top priority is the growing federal deficit and Klobuchar, he said, "is not part of the solution."

Throughout her term, Klobuchar has been a reliable Democratic vote, but also positioned herself as something of a centrist who often reaches out to Republicans on joint legislation built around consumer issues.

That has contributed to one of the highest job approval ratings in the state, with 60 percent of Minnesotans saying they approve of the job she's doing. More than half of Minnesotans say they have a favorable opinion of her, with 25 percent saying they view her unfavorably. Views on Bills were split evenly at 10 percent favorable and unfavorable, but the notable number comes in those who say they don't even recognize his name -- 62 percent.

Conducted by Mason-Dixon Polling for the Star Tribune between Sept. 17 and 19, pollsters interviewed 800 likely voters. The poll has a margin of error of plus or minus 3.5 percentage points.

Justin Buoen, Klobuchar's campaign manager, said Klobuchar's robust numbers reflect her record.

"These numbers show what we've known: Amy works hard for the people of Minnesota," Buoen said. "She does everything she can to put Minnesota first."

Bills' campaign manager Mike Osskopp dismissed the poll's results, saying that Democrats were overrepresented. The Minnesota Poll included 41 percent Democrats, 28 percent Republicans and 31 percent independents.

Osskopp said that a Bills internal poll found 35 percent self-identified Democrats, 25 percent Republicans and 40 percent independents. That poll, conducted early this month, showed Klobuchar with a 14 percentage point lead.

No poll since Klobuchar was elected in 2006 with nearly 60 percent of the vote has found the senator in danger of losing her seat and all public polls this year have found her with a substantial double-digit lead.

Klobuchar's continued popularity and Bills' inability to break through has led to a lackluster U.S. Senate campaign that has attracted little outside interest and few breakout moments. That's in sharp contrast to the 2008 Senate race -- a multimillion-dollar race so evenly split between Al Franken and Norm Coleman that it riveted national attention and wound up in a months-long recount.

Both are readying television ads.

Klobuchar plans to unleash a six-figure, statewide television ad campaign in the coming days. The Bills campaign has ads prepared, but Osskopp said this week that he thinks it is still too early to begin running ads.

Rachel E. Stassen-Berger Twitter: @rachelsb