(I'm cross-posting this from my blog in real-time, updates and all. Apologies for the cut-n-paste job, but I'm trying to update this thing in real-time.)
Based on numbers from the Indiana exit poll (via MSNBC), I determined that 13% of Clinton voters in Indiana actually plan to vote for John McCain in November, nearly three times the number of Obama voters who plan to vote for McCain.
As we assess the election returns tonight, it is imperative that we factor out pro-McCain voters for both candidates. The exit poll will continue to be tweaked as the night goes along, but based on these preliminary numbers, 13.4% of Clinton's total vote should be discounted and 4.9% of Obama's vote should be discounted.
Effectively, for Clinton to say she won without the help of pro-McCain Republicans, she needs about 53% of the vote.
Update: Just saw a chart on MSNBC that might explain why some of these pro-McCain voters are casting ballots for Clinton -- 58% of Republicans there think he is more likely to beat McCain than Clinton compared to 37% vice-versa.
Update 2: Via Ben Smith, Jonathan Chait takes another look at the data, estimating (correctly, I think) that about 7% of all Indiana voters were McCain supporters for Clinton. The number for Obama is about 2.5%.
Update 3: I've also written up how Republicans overall voted, regardless of whether they support Clinton. The key point is that 4.5% of Indiana voters were Republicans for Obama, exactly the same as it has been throughout the campaign, even when the GOP primary was still contested. Meanwhile, more than 5% were Republicans for Clinton, well more than twice her average in January and February primaries.
Update 4: Michiganliberal made the same point in a diary early this evening, a little before 5:30pm. I hadn't seen his/her diary when I posted this. I just went over there to give Michiganliberal some recc love.