Saturday's most important election may have been in Louisiana.
Donald Trump won Louisiana, but the primary was also the biggest piece of evidence that the anti-Trump vote is coalescing and something is happening in the race.
But both wins could potentially be explained away by Cruz simply out-organizing and outhustling Trump in caucus states. Trump's only commanding win in a caucus came in Nevada, a casino bastion where he has a large number of employees. He edged Cruz Saturday night in Kentucky too.
Kansas in particular is a state where moderate and conservative Republicans have been at war for years, with conservatives generally winning. The social conservatives who would prefer Cruz over Trump are well organized, having delivered the state for Rick Santorum in 2012 and electing Sam Brownback senator and then governor. Ben Carson is finally out of the running, making some additional evangelicals available to Cruz.
Maine was a strong state for Ron Paul in 2012. Mitt Romney only narrowly beat Paul under controversial circumstances. With Rand Paul now out of the race, some of those libertarians may have gravitated toward Cruz. Add some social conservatives and more traditional Republicans, and maybe that trumps Gov. Paul LePage's Trump endorsement and brings a caucus win.
Either way, the organizational dynamics of caucus states and the difficulty of reliably polling them limits our ability to draw conclusions from Cruz's wins. Maybe the events of the week — Mitt Romney's anti-Trump speech, the calls for strategic anti-Trump voting, the ongoing controversy over David Duke and the Ku Klux Klan, a debate in which Trump talked about his penis size, Trump skipping the Conservative Political Action Conference, the nation's largest gathering of conservative activists — helped Cruz win. Maybe Marco Rubio's Trump mockery hurt the billionaire without helping the Florida senator, much like Chris Christie's attack on Rubio.
But maybe it was simply a case of Cruz having a superior caucus organization and an appeal to constituencies that are well organized in those states.
Louisiana, however, was a primary rather than a caucus. Trump won the state on strength of early voters. He lost among people who showed up on election day. The RealClearPolitics polling average showed him leading by 15.6 percentage points, but he only carried Louisiana by 3.6 points.
Trump finished on the low end of his March polling, with a shade more than 41 percent of the vote, while Cruz overperformed even the high end at better than 37 percent.
If there was any sign that an anti-Trump vote is coming together, we saw it in Louisiana.
There are still some questions we don't know the answer to. Is this a real surge by Cruz or strategic anti-Trump voting that could later manifest itself in votes for Rubio in Florida or John Kasich in Michigan and Ohio? Does Trump have a closed state problem? He's mostly won in states where independents and even Democrats can vote (though unlike John McCain in 2000, he's had plurality support among self-described Republicans in exit polls in most of the places he's won). Can Louisiana be replicated in Mississippi?
Trump's subdued tone in his Super Saturday press conference and decision to call attention to Rubio's poor performance suggests he suspects something is amiss.
We pundits have repeatedly predicted the beginning of the end for Trump or Trump peaking for months without it happening. I'm reluctant to do it here. But if we do start to see real evidence that Trump is imploding, David Duke's home state of Louisiana may be where it all started.