House Speaker Paul D. Ryan (R-Wis.) has clearly had it with Donald Trump. On a day in which a dozen states hold presidential contests, Ryan felt he had no choice but to denounce the GOP front-runner for equivocating on whether to accept support from white supremacists.

"This party does not prey on people’s prejudices," Ryan told reporters Tuesday, referencing Trump in everything but name.

Ryan is obviously frustrated he even has to point out that a presidential candidate in his party shouldn't accept support from white supremacists. But we'd posit Ryan's frustration stems not just from what Trump says but also from how powerless Ryan knows he is to stop Trump, both from saying these kinds of things and from potentially winning the nomination.

Washington Republicans have been forced to essentially watch from the sidelines as much of their base swoons over a man many of them have come to despise. Party leaders quickly realized their words of condemnation are effectively useless, and oftentimes counter-productive, against a candidate who is channeling acute voter anger against the status quo -- i.e., them. Trump's appeal has evolved in such a bewildering way that the Republican Party, as The Fix's Chris Cillizza wrote Tuesday, has no idea what to do with Trump or his supporters.

That leaves Republicans like Ryan stuck in a Trump purgatory of sorts. The House speaker knows he has a responsibility to his party and his House colleagues to rap Trump when the GOP front-runner goes too far. If he doesn't say anything, Ryan faces valid questions from Democrats and Republicans alike about whether the Republican Party, writ large, agrees with Trump on this stuff. So he takes his medicine, criticized Trump, and hopes he can move on.

Ryan, for what it's worth, does come across as legitimately upset that Trump would hesitate even for a moment to denounce support from the likes of David Duke, a former Ku Klux Klan grand wizard in Louisiana who has encouraged people to vote for Trump.

Ryan's full comments Tuesday, via The Washington Post's Paul Kane:

"When I see something that runs counter to who we are as a party and as a country, I will speak up, so today I want to be very clear about something,” Ryan said. “If a person wants to be the nominee of the Republican Party, there can be no evasion and no games. They must reject any group or cause that is built on bigotry. This party does not prey on people’s prejudices. We appeal to their highest ideals. This is the party of Lincoln.”

But Ryan also undoubtedly knows that at this point, berating Trump in no uncertain terms probably won't do a thing to change Trump's front-runner status. In December, Ryan succinctly slammed Trump for suggesting the U.S. temporarily ban Muslims entering the country. "This is not conservatism," Ryan said at the time.

Speaker of the House Paul Ryan says the ban proposed by Donald Trump "is not what this country stands for." (AP)

Not to point out the obvious, but since then, Trump has gone onto win three of the four early-state nominating contests, has 49 percent of Republican primary voters' support in a new CNN/ORC poll and is the most likely candidate to win the Republican presidential nomination. It didn't slow him down one bit.

On Tuesday, Ryan even seemed to allude to the fact that he would rather not have to engage in these perfunctory denunciations of Trump, saying he hoped "this is the last time I need to speak out on this race.” But to Ryan's endless frustration, he knows it probably won't be -- and that what he says the next time around probably won't matter much, either.