Possibly picking up on an early poll breakdown by Chait, the Obama campaign sends out the following:

According to the latest exit polling data, 17% of voters in the Indiana primary today said they would vote for John McCain in a Clinton/McCain matchup.
 
41% of that number is constituted by people who voted Clinton in the primary but also indicated they will vote for McCain in the general election.
 
That comes out to just under 7% of the primary electorate the number that may be attributed to a “Limbaugh Effect.

 --Michael Crowley