Framing Science

Those looking for evidence of Limbaugh's influence pointed to Clinton's edge among Republicans in Indiana and North Carolina. In Indiana, 10 percent of Democratic primary voters described themselves as Republicans, a higher rate than in any state but Mississippi, and they went for Clinton by eight percentage points, according to exit polls. In North Carolina, they were 5 percent of the electorate, and went for her by 29 points.

By contrast, Obama won Republican voters, often by very large margins, in seven of the eight states where exit polls were able to report the group before the Texas and Ohio primaries on March 4, when Limbaugh first coaxed listeners to vote for Clinton.

Also notable was that in Indiana, six in 10 Republicans who supported Clinton on Tuesday said they would vote for presumptive GOP nominee John McCain over Clinton in the fall, if that were the matchup. By contrast, most Republicans who voted for Obama said they would back him against McCain. And a slight majority of Republicans who voted for Clinton in Indiana told pollsters that she does not share their values, raising further questions about why they supported her.

But at least as much data suggested that many Republicans voted for Clinton because the Democratic primary was the more meaningful one and because they simply preferred her to Obama. In Indiana, about nine in 10 GOP Clinton voters said she would make a better commander in chief, and more than six in 10 said she would have a better shot at beating McCain.

And Clinton's edge among Indiana Republicans was relatively small, if set against the broader racial divisions in the contest. Her eight-point advantage among Republicans, nearly all of whom are white in the state, was much narrower than it was among white Democrats, whom she won by nearly 2 to 1 over Obama.

Edward Carmines, a political scientist at Indiana University, said that he concluded from the data that while Operation Chaos "existed to some extent, I don't think it was a major factor."