We may have found the one poll question that communicates just how much of the Republican Party base is fully committed to President Trump.

In response to growing questions about his mental fitness, Trump tweeted a few weeks back that he wasn't just stable, but in fact a “very stable genius.” Polling since then has asked whether people feel Trump is indeed stable, but the new Washington Post-ABC News poll goes one step further and also asks whether Trump is a genius.

While Americans are about evenly split on his stability, the genius question is decidedly not an even split. Just 21 percent of American adults believe Trump's intellect rises to the level of a genius, while 73 percent say it does not.

But among that 21 percent is a substantial portion of Republican voters: 50 percent of them, all told. Just 40 percent of Republicans believe Trump is not a genius. So on balance more Republicans buy into Trump's claim than don't.

These Republicans apparently don't think Trump was just making a hyperbolic claim about his intellect; they actually believe he is a genius. Trump has been prosecuting this case for a while now, including pointing to his allegedly superior IQ. Given his seemingly erratic behavior and lack of interest in policy details, he's fought back hard against the idea that he is, as Secretary of State Rex Tillerson reportedly said after one particularly rough meeting, “a moron.” There was even a fake chart floating around the Internet suggesting that Trump's IQ was 156 and higher than most presidents.

“Genius,” of course, is a highly subjective term. But even taking that into account, I suspect that half of Republicans don't truly believe Trump is a genius. At the same time, that doesn't mean the poll isn't instructive.

Our increasing polarization has turned many of these survey questions into barometers — more or less — of partisanship. Republicans have almost always adopted Trump's positions, even if they aren't necessarily the traditionally conservative ones. Trump has moved the GOP significantly on issues such as free trade and has often increased the popularity of positions with which he disagrees, including on immigration. (Call it his “inverse Midas touch.") And when a poll question comes down to essentially siding with Trump or against him, the most devoted partisans will often choose sides accordingly, no matter how much they've truly thought the question through on its merits.

In this case, the Post-ABC poll question invoked Trump in the lead-in: “Trump has described himself as, quote, 'a very stable genius.' What's your own view: Do you think Trump is or is not a genius?” If the question had been simply, “Is Trump a genius?” support would likely have been lower. By invoking Trump, respondents who like Trump get to choose between either agreeing with him or labeling him a liar or exaggerator. The latter choice is not very attractive.

The last poll question that I think truly got at the size of the Never Not Trump crowd was a Monmouth University poll in August. It asked Trump supporters whether there was anything the president could do that would make them stop approving of him, and it showed 61 percent of those who approved of him said there was nothing. That amounted to 25 percent of all registered voters — 1 in 4 Americans — who basically gave Trump carte blanche to do whatever he wanted without risking their support. He could apparently commit genocide, homicide or even forsake every conservative position he holds without them so much as blinking.

Which, like with this new poll, isn't really true. But if anything, the new poll suggests slightly fewer Americans are truly that committed to Trump. Perhaps his hold on the base has weakened slightly.