Hillary Clinton wins Massachusetts Democratic primary

Hillary Clinton won Massachusetts' Democratic primary, according to multiple media reports — striking a blow in the heart of the Northeast, which has been Bernie Sanders' power base.

Sanders definitely needed a win in Massachusetts to keep his campaign alive. The state's heavily white, liberal Democratic electorate is very similar to the states where Sanders has been strongest: Iowa and New Hampshire. And Massachusetts was one of the states the Sanders campaign focused its energies on in the days leading up to Super Tuesday.

But polls in the days leading up to the election had Clinton with a slight lead. And she held it through election day.

What does this mean for the Democratic race?

The real measure of how important Massachusetts is to the broader Democratic primary battle is whether it makes it more likely or less likely that Bernie Sanders will be able to catch up to Hillary Clinton's support. Because the primary calendar is spread out, it's totally plausible that Clinton could come out to an early lead as her stronger states vote early — then watch it evaporate as pro-Sanders states turned out to the polls later. (Or vice versa.)

One way to figure out if Clinton's lead is temporary, or if Sanders is running out of time to close the gap, is to start backwards. If Sanders and Clinton had exactly equal amounts of support among all Democratic primary voters in America, what would the race look like right now? What would have happened in Iowa, New Hampshire, Nevada, and South Carolina, and what would happen in the Super Tuesday states tonight?

Nate Silver and the team at FiveThirtyEight have one way of estimating that. They use the demographics of each state to predict how much that state would "lean" toward Clinton or Sanders if the race were evenly tied nationally.

According to that model, if Sanders were tied with Clinton nationally, he'd be beating her by 11 points in Massachusetts. In other words, his actual performance in Massachusetts indicates that he's far behind Clinton nationally. Sanders might have pulled off a relatively-surprising win in Oklahoma during Super Tuesday, but his loss in Massachusetts bodes very poorly for his ability to stay in the race through the convention.