In a conference call over the weekend, that's what Clinton said happened, that the first Comey letter halted their momentum and the second pushed Donald Trump's voters to the polls.
But even so, that's not why she lost.
It's hard to tell from public polling what happened in the last two weeks. The RealClearPolitics polling average showed a big spike for Trump right after the first Comey letter, but our tracking poll with ABC News showed Trump improving his position against her for several days prior.
Trump saw a big jump in support from the polling average until Election Day, but it's not clear why. Was it a function of Comey? Was it something else?
The blog Emptywheel has a good analysis of Clinton's claim. Among the points made is that the last-minute surge could have been a function of Trump gaining support from undecideds or Gary Johnson supporters — something we'd noted a week before the election ended. At FiveThirtyEight, Nate Silver suggests that this was a big factor — with those deciding late in the election to back Trump over Clinton.
Whether or not that was because of the second Comey letter is, to some extent, unimportant. Clinton left the door open for Trump to the extent that his snatching the presidency from her on the back of 108,000 votes in the Upper Midwest was possible, however it happened. Our Jim Tankersley pointed out that Clinton failed to advertise as heavily in those Rust Belt states that she lost, which, paired with Clinton's failure to visit the states, suggests that they weren't high on her priority list.
I'd offer, though, that Clinton's mistake was more fundamental than that.
From the very first day, Post-ABC polling found that a majority of respondents didn't think Trump was qualified to be president. This was the angle of attack that Clinton's team decided to highlight, hammering again and again on Trump's temperament and obnoxious comments and disparagement of others. Emptywheel notes that Clinton's closing campaign ad reiterated this point again: Trump simply wasn't qualified to be president.
The problem is, that didn't keep people from voting for him.
In national exit polling conducted after last Tuesday, 6-in-10 voters said they didn't think Trump was qualified to be president. And yet one-fifth of those voters voted for him anyway.
Part of that is because of people who thought that neither candidate was qualified to be president. That group was 14 percent of the electorate, according to exit polls — and they picked Trump by a more than 4-to-1 margin.
Those figures only include people who turned out to vote. It seems clear that lower turnout among voters in her base contributed to Clinton's poor showing in the states that made a key difference (though, overall, she won the national popular vote). In Milwaukee County, Wis., Clinton currently leads by about the same margin as President Obama did in 2012, but got 50,000 fewer votes. In Wayne County, Mich., home of Detroit, Clinton got 517,000 votes to Obama's 595,000 four years ago. There are still votes to be counted in both states, but Clinton is poised to underperform.
But if nearly 1-in-5 voters both accepted Clinton's core argument about Trump but voted for him anyway, Clinton's campaign was in deep trouble before Comey did anything. Whether or not Comey's letters were the straw that broke the camel's back isn't clear. What's clear is that Comey provides an easy excuse, deservedly or not — and that the camel's back was already in pretty terrible shape.