Mourdock's favorable rating in the survey was even with his unfavorable rating in the high-30s, while Donnelly is much less known in the state but had better numbers, with 28 percent favorable to just 12 percent unfavorable.

The poll also showed the Tea Party as unpopular in the state, and Mourdock's calls for less bipartisan compromise to be similarly unpopular. If Donnelly can define Mourdock as an uncompromising Tea Party candidate while avoiding getting tied too tightly with President Obama, this could be a very tight race. The Hill rates the race a "toss-up."