There has been no recent nonpartisan polling of the race, though last Friday, after Mourdock made his remarks last week he put out another poll showing a tied race, while the Democratic Senatorial Campaign Committee released a poll showing Donnelly with a 7-point lead.

If Donnelly wins in the Republican-leaning state it would be a major blow to Republicans' hopes of taking control of the Senate. They need to win three seats for Senate control if Mitt Romney wins the presidency, and four if President Obama wins reelection.

Donnelly's poll of 600 likely voters was conducted by the Democratic Global Strategy Group from Oct. 28-30 and has a margin of error of 4 percent.