Democratic U.S. Sen. Tammy Baldwin leads her opponent, Republican state Sen. Leah Vukmir, by 11 points according to a Marquette University Law School poll released Tuesday.
Baldwin's lead has grown by 9 points since last month's poll, which had her up by just 2 points among likely voters.
The latest poll was conducted Sept. 12-16, with a sample that included more Democrats than a poll released in August. The margin of error among likely voters was 4.4 points.
Forty-eight percent of likely voters hold a favorable opinion of Baldwin, compared with 40 percent who view her unfavorably and 12 percent who don't have an opinion.
Thirty-six percent of likely voters still don't have an opinion on Vukmir, while 26 percent view her favorably and 38 percent view her unfavorably.
Vukmir, a registered nurse, was first elected to the state Assembly in 2002 and to the state Senate in 2010. Baldwin was elected to the state Assembly in 1992, to the U.S. House of Representatives in 1998 and to the U.S. Senate in 2012.
According to data compiled the Center for Responsive Politics, the Wisconsin Senate race is among the most expensive in the country, with nearly $40 million spent by candidates and outside groups.