Just when you thought this primary season couldn’t get any more unusual for Republicans, in a stunning turnaround of fortunes, incumbent Senator Thad Cochran, who was down in the polls across the board, managed to fend off Tea Party favorite Chris McDaniel. Many of the polls had Cochran down by eight to nine points, but his victory with 51 percent of the vote, or about 7,000 votes, stunned most observers.

So how did Cochran pull off this amazing comeback in such a short time, when everyone had him down by almost double digits? Over at Politico the usual suspect comes to mind: money:

Outside spending in the race was close to even, but much of the TV money for McDaniel was spent in sloppy or inefficient ways. While he enjoyed heavy support from the national Club for Growth and the Senate Conservatives Fund, McDaniel also saw the airwaves crowded by screwball, out-of-right field ads by groups seeking to link Cochran to the release of Taliban prisoners from Guantanamo, or using the sound effects of bleating sheep to mock Cochran for a remark about “indecent” activities with animals. He spent valuable time campaigning with politically marginal figures like former game-show host Chuck Woolery.

I disagree completely. If one looks at the polls that were coming from the Cantor-Brat race, they had Brat down by double digits, and the Brat campaign was widely outspent by the Cantor team. While it is easy to blame money, after examining the numbers, I agree with Harry Enten over at FiveThirtyEight.

According to Enten’s article:

About 375,000 voters showed up Tuesday compared with 318,904 on June 3, an increase of more than 17 percent. Cochran raised his vote total by more than 38,000 votes, while McDaniel pulled in only an additional 30,000. That was more than enough to erase McDaniel’s 1,386 vote lead in the first round.

So who were these new voters? Did they influence the election? The answer: they were African-American voters in Hinds County, which was crucial in both the primary and the runoff. Just how important were these votes?

Cochran’s campaign explicitly tried to increase his turnout in the runoff by bringing Democratic-leaning African-Americans to the polls. Mississippi primaries are open, so all voters were welcome on Tuesday so long as they hadn’t voted in the Democratic primary three weeks ago.

Also:

Take Hinds County, where African-Americans make up 69 percent of the population, as an example. Cochran increased his vote total there by about 7,000 votes from the first round of the primary and his share of the vote by a little over 6 percentage points to 72 percent on Tuesday.

While the article’s graph shows correlation between African-American voters and Cochran’s share of the vote, it does not with McDaniel:

McDaniel’s results, on the other hand, show a different pattern. If 30 percent of Cochran’s vote increase can be explained by the racial makeup of the county, less than 1 percent of McDaniel’s vote increase can (at least according to the coefficients of determination).

How much of a difference did this make?

Keep in mind, though, that the pre-election polls had McDaniel ahead by around 8 points. It seems plausible that the reason they got the race wrong was because they were modeling an electorate that looked a lot more like the first round of the GOP primary instead of the runoff. That certainly makes sense given what I found. The analysis here suggests that Cochran may very well have won because he was able to get traditionally Democratic voters to cast their ballots for him.

This equates to a ten-point swing across the state. While Cochran’s motives to get those votes might be questionable, the fact is that many of the polls and pollsters were correct in their projections, but did not account for the Democratic turnout. Then again, it doesn’t matter what the polls say, as we saw with Brat. It matters what happens on Election Day.