Bernie Sanders got a crucial victory on Super Tuesday, winning Oklahoma's Democratic primary.
Oklahoma is actually one of the most important contests of the night for the Democratic primary race. It's one of the few whose outcome was genuinely in question going into Super Tuesday. More importantly, it was an important test of whether Bernie Sanders' early victory in New Hampshire (and his tying Hillary Clinton in Iowa) was indicative of a lasting appeal within the Democratic Party, at least among white voters.
Sanders spent serious time in Oklahoma in the days before the primary, and his campaign devoted serious resources to its operations there. The Sanders team very much wanted to use a victory here to show that he hadn't lost momentum since New Hampshire among the voters who'd supported him most. And they got what they wanted.
What does this mean for the Democratic race?
The real measure of how important Oklahoma 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 4 points in Oklahoma. This is one reason why the Sanders campaign worked so hard there. And it's one reason why they should be breathing a huge sigh of relief that they won.