U.S. Senate Marquette poll

U.S. Sen. Ron Johnson, left, and Democrat Russ Feingold, right, meet before their second and final debate Tuesday in Milwaukee. 

Days before the election, Wisconsin’s U.S. Senate race is a statistical toss-up, according to the final Marquette Law School Poll of the 2016 campaign.

The poll finds Democrat Russ Feingold with 45 percent support and Republican incumbent Sen. Ron Johnson at 44 percent — the narrowest margin between the candidates recorded by the poll during the campaign.

The results ensure both sides will pour all available resources into the final days of a race that could determine which party controls the U.S. Senate in 2017.

“It’s right on the knife’s edge and could go either way,” Marquette pollster Charles Franklin said after announcing the results.

[Final Marquette poll shows Hillary Clinton holding six-point lead in Wisconsin]Three percent of poll respondents supported the Libertarian candidate, Phil Anderson. The poll was conducted Oct. 26-31, interviewed 1,255 likely voters and has a margin of error of 3.5 points.

The previous Marquette poll, conducted Oct. 6-9, also had Feingold leading Johnson within the poll’s margin of error, 46 percent to 44 percent among likely voters.

Other public polls of the race in October have shown Feingold leading by between 2 and 12 points. One public poll, conducted by Loras College, has shown Johnson leading.

In a potentially troubling sign for Feingold, the new Marquette poll shows self-identified independent voters moving toward Johnson. Forty-six percent of independents favored Johnson compared to 40 percent who backed Feingold — a reversal from the previous poll in which independents preferred Feingold, 44-37.

Johnson’s campaign hailed Wednesday’s results as a sign it is gaining steam.

“This race is a dead heat and the momentum is clearly with Ron Johnson,” Johnson spokesman Brian Reisinger said in a statement.

[Track the latest Wisconsin polls for president, senate]Feingold campaign spokesman Michael Tyler said Feingold retains a clear advantage. Tyler added that corporate and billionaire-backed groups are dumping millions into Wisconsin “with negative attacks in a last-ditch effort to keep (Johnson) in Washington to protect their interests.”

Millions of dollars of ads sponsored by outside groups have poured into the race in recent days, most of it supporting Johnson. This week, millions in new advertising to aid Johnson was announced by Americans for Prosperity, backed by the billionaire Koch brothers, and Reform Wisconsin Fund, a super PAC funded by a group bankrolled almost entirely by Afton billionaire Diane Hendricks, co-founder of ABC Supply Co. in Beloit.

Moments after the Marquette poll release, Feingold’s campaign launched a fundraising email to supporters with the poll results in the subject line.

Also Wednesday, the candidates rolled out a slate of TV ads as part of their closing pitch to voters.

Johnson’s campaign debuted two ads: One featuring a seated Johnson speaking into the camera about what Americans share in common. The other ad blasts Feingold for his 34 years in elected office “with very few accomplishments and a lot of broken promises.”

Feingold’s campaign released an upbeat spot in which Feingold talks about what he heard from Wisconsinites on his tours of the state’s 72 counties — while supporters file out of a campaign van, interjecting with criticisms of Johnson’s record.

Feingold was campaigning Wednesday in Milwaukee with Vermont Sen. Bernie Sanders.

The candidates also were planning key stops for the campaign’s last weekend.

Johnson — who campaigned in Eau Claire on Tuesday with GOP nominee Donald Trump — was set to embark on a bus tour with U.S. House Speaker Paul Ryan, R-Janesville and Gov. Scott Walker.

Feingold was scheduled to appear with Vice President Joe Biden at an early voting event in Madison on Friday morning.

The track record of the Marquette poll is why it’s regarded by many political observers as the gold standard for polling in Wisconsin. In the state’s most recent U.S. Senate race in 2012, the final Marquette poll came within 1.5 percentage points of predicting the outcome, in which Democrat Tammy Baldwin beat Republican Tommy Thompson 51 percent to 46 percent.

The latest poll results suggest Johnson is beginning to separate himself from Trump — which some consider a requisite for Johnson to prevail.

After months of polling showed Johnson at or below the level of support for Trump in Wisconsin, the new poll finds Johnson running well ahead of his party’s presidential nominee, who trails Democrat Hillary Clinton in the poll, 46 percent to 40 percent.

Capital W: Plug in to Wisconsin politics

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Percentage of respondents who would vote for candidates in the most recent Wisconsin polls.