This weekend's ABC News/Washington Post poll was very bad news for the Donald Trump campaign. Not only did it have Hillary Clinton with a comfortable, 50-42, lead over Trump in the head-to-head matchup, it provided more evidence that the Clinton campaign has done a better job corralling the core Democratic groups than the Trump team has done with core Republican groups.

The ABC/WaPo poll offers extensive breakdowns of vote preferences by demographic group, which can be compared to the 2012 presidential exit poll. Doing that gives a good sense of how well each candidate is performing with the base Democratic or Republican groups, as well as groups that roughly split their votes. (To account for the fact that a large chunk of voters remain undecided, we'll compare margins in the ABC/WaPo poll to 2012 exit poll margins.)

To start, let's look at how Trump is doing with core Republican groups relative to Mitt Romney's performance in 2012.

On balance, Trump is doing worse—much worse, in fact—with the essential groups of the Republican coalition. ABC/WaPo actually has him losing several groups that Romney won handily—the middle aged, elderly, and white Catholic vote.

His underperformance among white voters may not appear terrible at first glance, but remember: Whites will comprise about 70 percent of the electorate, and his appeal to non-whites is limited, so Trump will have to improve on Romney's margin among whites if he hopes to win. Right now, he's not even close.

Note also how badly Trump is doing with Republicans and conservatives, which is consistent with my observations last week. This suggests that the Republican National Convention was basically unsuccessful. One of the core tasks of the contemporary convention is to bind the wounds from the primaries and to bring the party base together in preparation for the fall campaign. Though Trump is doing all right with conservatives and Republicans, a very large share of them are not yet on board with him. Perhaps they will join at a later date, but right now it simply has not happened. He needs to do better with these core groups if he is going to win.

The good news for Trump is that he's doing better with men in this poll than Romney did in 2012, which—given his relatively weak share of the white vote—might indicate surprising strength among non-white men. Of course, this is just one poll, with a large sampling error for such subgroups, so caution is warranted.

Meanwhile, how is Clinton doing with the core Democratic voters, relative to Barack Obama's performance in 2012?

On balance, Clinton looks to be in solid shape with her base, and the Democratic National Convention appears to have been a success. She's about as strong as Obama with liberals, moderates and Democrats. She's struggling a little bit (relatively speaking) with Obama's most loyal voters—non-whites and young people—but she has more than made up for that among women voters.

Finally, what about the groups that are roughly in the middle of the electorate?

This is a very interesting set of numbers. In 2012 the political cleavages among education groups were pretty minimal. Post-graduates broke heavily toward Obama, but everybody else was more or less split evenly. This cycle, there is a substantial "education gap." The non-college educated are falling roughly in line with where they were in 2012, but college-educated voters are breaking heavily against Trump. Given that they will comprise roughly half of the electorate this cycle, there is no way to win without doing better than them.

Taking these two three charts together, it is pretty clear that Trump's underperformance with his base voters primarily has to do with female and college-educated Republicans—who are either still undecided, or have bolted to Clinton's camp. My hunch is that, for instance, white Catholics per se do not have a problem with Trump, but college-educated white Catholics do. Ditto for female white Catholics. His margins are just so bad with these two crosscutting swaths of voters that it is probably holding down his numbers among most demographic categories.

If it were 1916, Trump would be a shoo-in for victory. But in 2016, the electorate will be dominated by females and the college educated, and they seem to hate Trump. He has to turn it around with them, or he will be "dumped like a dog" in November.