Republicans fighting to hold Congress will learn something Tuesday about their party's capacity for self-control.
In West Virginia, a critical target for preserving their Senate majority, Republican primary voters are considering a wealthy coal executive who recently completed a prison term resulting from his role in a mine explosion that killed 29 people. The executive, Don Blankenship, has smeared Senate GOP leader Mitch McConnell and his "China person" in-laws in a crude campaign he calls "Trumpier than Trump."
A Blankenship victory, which polls suggest is possible, would improve the chances that vulnerable Democratic Sen. Joe Manchin could hold his seat in November's general election. And it would signal anew, as 2018 primaries begin in earnest, that President Donald Trump has helped revive the penchant for self-inflicted wounds that limited GOP gains in Obama-era Senate campaigns.
In 2010 and 2012, the weak Senate nominees who emerged from GOP primaries in states such as Nevada, Missouri, Indiana and Delaware helped Democrats extend control of the chamber. In 2014, the GOP rallied behind McConnell's efforts to advance more electable candidates and regained the majority.
But now the rank-and-file voters who responded to Trump's gut-level appeals are considering new primary choices in a GOP under the president's control. Their decisions, in lower-profile House races as well as more conspicuous Senate contests, will shape the party's ability to resist the Democrats' national momentum this fall.
Their passions have already narrowed the Republican margin for error. In Alabama's special election last November, the nomination of accused child molester Roy Moore allowed Democrat Doug Jones to win a Senate seat in one of the nation's most conservative states.
Intraparty resistance has driven two of the 51 GOP Senate incumbents, Jeff Flake of Arizona and Bob Corker of Tennessee, to not seek re-election.
In Tennessee, some polls have shown a former Democratic governor leading a Republican congresswoman. In Arizona, the candidate Senate GOP leaders prefer faces fierce primary opposition that includes a former sheriff pardoned by Trump for a crime stemming from his conflicts with Latino immigrants.
Even the most eminent Republican politicians can't avoid the primary cauldron. In Utah, the 2012 GOP presidential nominee Mitt Romney has been forced into a June primary after a state legislator captured more votes at a party convention.
Democrats face their own intraparty disputes but have proven far more successful at tempering them in the name of electoral pragmatism. Thus moderate incumbent Sen. Joe Donnelly of Indiana, who has voted with Trump more than half the time over the last 16 months, faces no Democratic opposition in Tuesday's Indiana primary.
Republicans, by contrast, have endured a bitter contest pitting wealthy business executive Mike Braun against two House members, Luke Messer and Todd Rokita. Tuesday's winner faces a challenge in uniting the GOP base against Donnelly in November.
Superior party unity has even given Democrats an outside shot of picking up a Senate seat this fall in Mississippi, another conservative Southern state that they haven't carried for president for four decades. While Democrats rally behind Mike Espy, a black former congressman and presidential Cabinet member, Republicans face a bitter contest between appointed incumbent Sen. Cindy Hyde-Smith and state legislator Chris McDaniel. The state's primary is scheduled for June 5.
McConnell has appealed to Trump for help with the GOP's problem. At his urging, the president on Monday intervened in the West Virginia primary.
"Don Blankenship, currently running for Senate, can't win the general election in your state," Trump told West Virginians on Twitter. "No way! Remember Alabama."
Republican leaders in Washington remember Alabama well. Trump backed appointed incumbent Luther Strange in the Senate primary, but only tepidly.
"I may have made a mistake" in not favoring Moore, Trump declared before the contest was over. Moore's subsequent defeat is the reason Democrats need to gain only two seats, not three, to turn 2018 Senate Minority Leader Chuck Schumer into the 2019 Senate majority leader.