Many Democrats have a shorthand explanation for Clinton’s defeat: Her base didn’t turn out, Donald Trump’s did and the difference was too much to overcome.

But new information shows that Clinton had a much bigger problem with voters who had supported President Barack Obama in 2012 but backed Trump four years later.

Those Obama-Trump voters, in fact, effectively accounted for more than two-thirds of the reason Clinton lost, according to Matt Canter, a senior vice president of the Democratic political firm Global Strategy Group. In his group’s analysis, about 70 percent of Clinton’s failure to reach Obama’s vote total in 2012 was because she lost these voters.