Pretty much the only reason conservatives have for supporting Donald Trump is the Supreme Court. "Think of SCOTUS!" is a superficially compelling argument. But only superficially.

For starters, conservatives have no reason—none—to believe that Trump would appoint a conservative justice. I point you here to Ramesh Ponnuru's depressingly compelling assessment of Trump's views of the high court:

Trump's word is meaningless. He stiffs creditors and contractors. He lies about matters small and large: about having told Republicans to hold their convention in Ohio, about letters he supposedly received from the NFL and about having opposed the Iraq war from the start. Trump isn't even trustworthy on his signature issue of immigration: He flip-flopped twice in one day during the campaign about whether high-skilled immigrants should be kept out as a threat to American jobs or welcomed as a boon to our economy. Why would he keep his word on the courts? He doesn't care about the Constitution or the proper role of judges. When he talks about the Constitution, it's glibly and dismissively. When it's suggested that the Constitution might pose an obstacle to his plans, he says it "doesn't give us the right to commit suicide." He knows almost nothing about the law: He can't tell the difference between a judicial opinion and a bill. The few times he has taken an interest in constitutional issues, he has been on the other side from most conservatives. He thinks the government should have broad power to take people's property and give it to developers; they don't. He has used courts as a weapon to silence critics, and thinks it should be easier to use them that way. Most conservatives find that record and that idea appalling. If President Trump asks his aides to find him a judge who agrees with him on these issues, they will start by scrapping his list.

The next part of "Remember the SCOTUS!" insists that Republican senators—the same group of sell-out, RINO elites that are always being blamed for Trump's rise—will somehow discover the backbone to force Trump into picking a conservative. What in the history of Trump's relationship with institutional Republicans might lead one to believe that they, the GOP, could bend Trump to their will? Search me.

Last week David Frum wondered if the dynamic might not run the other way, actually: "Isn't it more likely that President Trump will choose his judicial nominees to spite Paul Ryan and Mitch McConnell than to please them?"

After watching Trump attack Paul Ryan, Kelly Ayotte, and John McCain last week, the answer to this question has got to be—at least—maybe?

And here's Ponnuru again, gaming out a much more plausible scenario for what Trump might do:

To get a conservative on the Supreme Court would require a President Trump to wage an ideological war with Senate Democrats, even though he says he would prefer to be a dealmaker, and even though that war would turn on issues for which he has never in his life shown the slightest concern. Instead of making good on his promise, he could cut a deal with the Democrats. His nominee could then win confirmation with the support of most Democrats, moderate Republicans, and some conservative Republicans who will want to be on the same side as Trump.

But the biggest problem with the "Remember the SCOTUS!" argument is that it's such a blanket theory that it's ultimately useless. Should you vote for any candidate with an R next to his or her name, because SCOTUS?

What if Hillary Clinton had won the Republican nomination in 2016? This might sound crazy now, but if, in June of 2008, I had told you that either Donald Trump (the liberal reality TV star) or Hillary Clinton (a moderate, hawkish Democrat who had just fought Barack Obama to a stand-still using a base of white, working-class voters) would some day be the Republican nominee, you wouldn't have been so sure.

So if Hillary Clinton had been the Republican nominee in 2016, would you have had to vote for her because of the Supreme Court? Surely, at some point, the quality of the candidate matters enough to cause the argument to break down.

Or let me put it another way: Suppose that you're a Republican in Louisiana and David Duke gets to the runoff against the Democratic candidate. Suppose further that Donald Trump looks set to win the White House and the Senate map suggests that the Louisiana seat could be the one to get Republicans to a majority in the Senate. Which would then give them to power to control the judiciary committee and get a conservative justice through.

Would you buy the argument that you have to vote for David Duke? Remember the SCOTUS!

To my mind, the best ethic I've seen for voting in the age of Clinton-Trump came from Matthew Franck a few weeks ago:

After a lifetime of studying politics, I have finally, thanks to the electoral annus horribilis of 2016, arrived at an ethic of voting that I can defend against all rival ethics. It is simply this: Vote as if your ballot determines nothing whatsoever—except the shape of your own character. Vote as if the public consequences of your action weigh nothing next to the private consequences. The country will go whither it will go, when all the votes are counted. What should matter the most to you is whither you will go, on and after this November's election day.

The chances that any one vote will have an effect on the Supreme Court is infinitely small. Like winning the Powerball. Once a year, for the rest of your life

The chances that rationalizing yourself into voting for a man like Trump will have an effect on you are a good bit higher.