If this poll accurately reflects the US electorate, get ready for the mother of all gender gaps (so to speak) in November if Donald Trump wins the Republican presidential nomination. The frontrunner has a major problem with women, according to this Reuters-Ipsos poll conducted over the first half of March, and it has gotten worse rather than better over the last six months. Half of all women have a “very unfavorable” view of Trump, in an election that could pit him against the first female major-party nominee:

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. The survey was taken from March 1-15, and included 5,400 respondents.

The rise in anti-Trump sentiment among women could pose a problem for the New York billionaire in his quest for the White House. Women form just over half of the U.S. population, and they have turned out at higher rates than men in every election since 1996, according to the U.S. Census Bureau.

“If the presidential election were tomorrow, women would be a big problem for Trump,” Republican strategist David Carney said. “But he has time to fix it.”

In head-to-head polling, Reuters puts the gender gap between Trump and Hillary Clinton into double digits:

If the GOP frontrunner were to run against Democratic hopeful Hillary Clinton in the general election, likely women voters would support Clinton over Trump by nearly 14 percentage points, according to the March polling data. Among men, Clinton would win by about 5 percentage points.

I asked Reuters for a statement on methodology, and they provided this:

Margin of error: The credibility interval for our polls on women who give Trump the lowest level of favorability – aka “very unfavorable” – is 1.9 percentage points in March and 1.6 percentage points in October.

Sample sizes and dates: The March poll included 3,477 responses from March 1 to March 15. The October poll included 5,093 responses from Oct. 1 to Oct. 31.

It’s an interesting result, especially since the same polling data for Reuters’ national tracking poll suggests that Trump does better among women at the moment than his Republican rivals in the GOP primaries, at least. Filtering down to March 1-15 and selecting women only across all political affiliations, a third of 1,997 respondents support Trump for the GOP nomination, while only 16% support Ted Cruz. Nearly 30% wouldn’t vote at all. When narrowed further to only Republican and independent voters (1,632 respondents), Trump gets 39%, Cruz gets 18.3%, and 18.9% wouldn’t vote at all. (Note that this poll included Marco Rubio and Ben Carson for at least part of the period.)

Even without the gender gap, Trump has major favorability issues in Reuters’ tracking polls. Once again filtering for those who participated in 2012, 39.5% of respondents view him very unfavorably, 6.9% somewhat unfavorably, and another 9.2% lean toward unfavorable, for a total unfavorability of 55.6%. He gets only 18.2% for “very favorable,” with a total favorability of 44.4%.

However, when it comes to the head-to-head matchup, the tracking poll shows Trump a distant second to Hillary, 41.1/34, with a quarter of respondents declaring that they’ll skip the election altogether. That narrows slightly when filtering out all those who didn’t vote for either Barack Obama or Mitt Romney in 2012, but Hillary still leads 46.2/39.7, and 14% of those who voted in 2012 say they won’t be back in 2016. Among men who voted in 2012, Hillary only has a slight edge, 44/43.5, but among women who voted in 2012, it expands to 48.5/35.8.

Don’t forget that the gender gap in 2012 was much narrower. Women made up 53% of the electorate and broke 55/44 for Obama, while men went for Romney 52/45 for a net gap of -4 for the GOP. Right now, we’d be looking at a net gap of -13.2 among those who voted in 2012. That has the makings of a disaster for Republicans in November if it doesn’t change, one that could roll well down the ballot.

There is certainly time to fix this, and head-to-head polling is still somewhat fraught at this stage with other emotional baggage from the primaries. Also, Reuters does not have similar data readily available to compare Trump against Ted Cruz or John Kasich, which makes it a little tough to argue on a data basis that either would substantially improve the GOP’s chances in the fall. However, this is still a big red flag for Republicans, especially given that they will likely face off against a woman at the top of the opposing ticket.