MADISON (AP) -- Democratic U.S. Sen. Tammy Baldwin's approval rating is 37 as she runs for re-election, while most voters don't know enough about either of her Republican challengers to form an opinion.
The Marquette University Law School poll released Monday shows that her rating is statistically unchanged from nine months ago when it was 38 percent.
Since then, more than $3 million has been spent on television ads by conservative groups opposing her in the Senate race.
Her disapproval rating since June has gone from 38 percent to 39 percent.
Baldwin is being challenged by Republican state Sen. Leah Vukmir and Delafield businessman Kevin Nicholson. The poll shows more than 80 percent of voters don't know enough about either of them to form an opinion.
The poll surveyed 800 registered voters between Feb. 25 and Thursday and had a margin of error of plus or minus 4.5 percentage points.