MADISON, Wis. — Less than a month before Wisconsin's Aug. 14 primary, roughly a third of voters are still undecided in the Democratic primary race for governor and Republican contest for U.S. Senate, according to the latest Marquette University Law School poll released Wednesday.

The poll , which was conducted from July 11 through Sunday, showed that 30 percent were undecided in the Senate race, which was unchanged from last month. It also showed that 38 percent of those surveyed were undecided in the Democratic primary, which was up from 34 percent last month.

That gives all of the candidates hope to make a move. As the poll results were being announced, Matt Flynn released the first television ad of the Democratic gubernatorial primary. Republican Gov. Scott Walker has been running ads for weeks touting his record and millions have already been spent on ads in the Senate race.

Among the eight Democrats running in the primary, state Superintendent Tony Evers led the field with 31 percent in the latest poll, with the other seven trailing far behind, at around 5 percent. Evers' support was higher than the other seven candidates combined, but still less than the percentage of undecided voters.

Evers certainly has an advantage, but there's "lots of undecideds," said the poll's director Charles Franklin.

Flynn, who was at 5 percent in the poll, touts his opposition to the Foxconn Technology Group project in the ad, calling it a "corporate welfare giveaway." A retired attorney, he vows as governor to go to court to stop the deal that Walker negotiated. Flynn spokesman Bryan Kennedy said the ad will begin on Friday and run in Milwaukee, Madison, Green Bay and a fourth to-be-determined market.

The poll is the latest measurement of strength for candidates heading into the primary. Another was campaign finance reports that were submitted earlier this week. Those showed that former state Rep. Kelda Roys had the most cash on hand, with $668,000, followed by Flynn, the former Democratic Party director, at $403,000, and state firefighter union leader Mahlon Mitchell, with $368,000.

Candidates will need money to buy television ads in the final weeks of the race to reach voters who the poll shows remain largely in the dark about who is running.

As for Walker, the poll put his approval rating at 47 percent support, which was down from 49 percent last month.

In the Republican Senate race, the poll showed the contest about even with state Sen. Leah Vukmir at 34 percent and Kevin Nicholson at 32 percent, with a 7-point margin of error. Vukmir appears to have the momentum, seeing her support increase 15 points from 19 percent in March. Nicholson's has gone up just 4 points, from 28 percent in March.

The winner will advance to face Democratic Sen. Tammy Baldwin. The poll showed her favorability rating unchanged since June at 41 percent.

The poll surveyed 800 registered voters. It has a margin of error of plus or minus 4.1 percentage points, although that increases to 6.6 percentage points for questions targeting Democratic primary voters and 7 points for Republicans.

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This story has been corrected to show that 34 percent of those surveyed backed Leah Vukmir and 32 percent backed Kevin Nicholson, not the other way around.