Trump loves the ladies. (Photo by Jabin Botsford/The Washington Post)

There are lots of reasons for Republicans to be worried about having Donald Trump as their presidential nominee, and new polling data out from Reuters today shows one of the ways a Trump nomination could be fatal:

Real estate billionaire Donald Trump’s coarse rhetoric has won him some fans, but there’s at least one large group in America that is increasingly unimpressed: women.

Half of U.S. women say they have a “very unfavorable” view of the front-runner for the Republican presidential nomination, according to Reuters/Ipsos polling, up from the 40 percent who felt that way in October.

This is only one data set (albeit a large one; it’s based on two weeks’ worth of polling and includes 5,400 respondents), and things can and probably will change over the course of the next few months. But we need to appreciate just how dramatic these numbers are. Half of all women voters at the moment feel not just somewhat or slightly unfavorable toward Trump, but very unfavorable toward him.

So I’ll go ahead right now and predict that if Trump and Hillary Clinton are the nominees, the 2016 vote is going to show the largest gender gap of any election in our history.

There are multiple reasons why. To begin with, women are more likely to be Democrats; it’s been 28 years since a Republican won a majority of women voters. Then there’s Trump’s particularly crude sexism, aimed at celebrities and journalists and any woman he doesn’t like. Then there’s the fact that he’s someone who starts looking around for a new, younger wife when his current one hits her forties. Then there are incidents like the one where his campaign manager manhandled a female reporter, then denied it happened while he and his boss basically called her a crazy bitch. Then there’s his frequent display of a kind of anxious masculinity, in which he talks about the size of his penis and poses as a tough guy eager to beat up protesters, which women voters are bound to find repellent.

In sum, it isn’t a matter of a comment here or an idea there — Trump has already managed to alienate women voters in a dozen different ways, which is going to make that deficit particularly difficult to undo.

Now let’s place this in some historical context. Gallup has data that goes back the farthest on the question of the gender gap, so I used their figures to create this graph showing the size of the gap over elections in the last half-century (Gallup’s numbers occasionally deviate from the exit polls, but not by much). The numbers on the chart are the advantage for the Democratic candidate for each group, so positive numbers mean the Democrat led among that group, and negative numbers mean the Republican led:

What we see overall is that with the exception of 1984, until 1992 men’s votes and women’s votes were remarkably similar. Beginning in 1996, the two diverge. But it’s important to realize that a gender gap isn’t necessarily a problem for Republicans in and of itself, even though we often talk about it as though it were. If the Republican wins among men by 10 points and loses among women by 5 points, then there’s a significant gap, but the Republican still wins the election. It’s better to think about it as two gaps, one among each gender. The sizes of both of those gaps can determine who wins (keeping in mind that overall, women vote at somewhat higher rates than men).

So for instance, the 2012 election showed a gap on both sides, totaling up to the largest Gallup ever recorded, at 20 points. The total gap was smaller in 2008 at 14 points, but Obama won by a larger margin in 2008 because he pulled even with John McCain among men. Four years later, the gap among women remained almost the same, but men were much more likely to vote for Mitt Romney.

To return to this year’s election, it seems somewhere between unlikely and impossible that Trump will be able to dramatically change his image among women. At some point he may realize this is a problem and try to do something about it, but given how he has campaigned so far, whatever he attempts will probably be neither subtle nor effective. I’m guessing his message will be something along the lines of, “Look, I love women. Totally love them. I’ll be great for the women.”

Which will be about as effective as when he says the same thing to Hispanics. Just the other day his campaign put out a video attacking Clinton that featured Vladimir Putin and someone from ISIS, and the message seemed to be nothing more than, “We can’t elect a girl president, can we?” And we can be sure that when Trump starts attacking Clinton in earnest, a lot of of what he says is going to drive women voters further and further away.

Hillary Clinton has her own image problems, of course. But as all this evolves, there’s a good chance that Trump will not only turn off women, he’ll also turn them out — to vote against him (and for the first woman president). The only way he could overcome the resulting deficit will be if he’s able to expand the gender gap on the other side, winning men by an even greater margin than he loses women.

Can he do that? The challenge for him is that the kind of man who cheers Donald Trump is probably already a Republican. Maybe there are millions of backwards-hat-wearing frat boys just waiting out there to vote for the first time, and that will pump Trump’s numbers up with men. But I doubt it.