Senator Bernie Sanders easily won the Democratic primary in West Virginia, the first of a string of potentially strong showings this month that may drag out, but not block, front-runner Hillary Clinton's march towards the Democratic nomination.
Additionally, Republican Donald Trump won Republican primaries in West Virginia and Nebraska - virtually foregone conclusions given that he was the only Republican remaining in the race.
Heading into today, Clinton held a formidable lead in delegates, and because delegates will be awarded proportionally, Sanders's West Virginia victory was not expected to make much of a dent in that lead.
However, his enduring popularity, large rallies and insistence on staying in the race until the Democratic convention in July have highlighted some of Clinton's weaknesses and prevented her from fully turning her attention to the general-election contest against Trump.
"West Virginia is a working-class state, and like many other states in this country, including Oregon, working people are hurting," Sanders said at a rally in Salem, Oregon. "And what the people of West Virginia said tonight, and I believe the people of Oregon will say next week, is that we need an economy that works for all of us not just the 1 percent."
Sanders's advantage over Clinton in West Virginia was clear in preliminary exit polling. According to data published by CNN, roughly one in three Democratic voters identified as independents - and only one in four wants the next president to continue President Barack Obama's policies. That number represents less than half the average across previous primaries this year. Clinton has promised repeatedly to continue and build on many of Obama's policies.
Sanders also benefited from support among Democratic primary voters who said they would favour Trump over Clinton or Sanders in a general election. Roughly one in three primary voters said they would back Trump in the general over Clinton, and Sanders won two-thirds of their votes.
Clinton was weighed down by her own troubles. Three in 10 Democratic primary voters said they or a family member were employed in the coal industry, and Sanders won those voters by more than 20 percentage points. Ahead of the primary, Clinton was forced to reckon with comments she had made earlier in the campaign about putting the coal industry "out of business".
Sanders used the West Virginia victory as a rationale to stay in the race "until the last vote is cast". Less than 15 minutes after the polls closed, Sanders sent out an email to supporters declaring victory and asking for money to help him in the next two contests in Kentucky and Oregon.
Recent polls show Sanders likely to perform well in a string of subsequent primaries this month in Oregon, Kentucky and Washington - states with smaller minority populations where Clinton may face similar challenges as in the West Virginia electorate.
Nevertheless, Clinton may have found a purpose to these upcoming contests in addition to trying to improve her performance against Sanders: to connect with the working-class white voters who may be crucial in a general-election match-up against Trump.