Donald Trump's victory in South Carolina, where he defeated Nikki Haley by 20 points in her home state, is being treated as a significant triumph. In one sense, it indeed was. Trump's victory was so decisive that networks called it within minutes of the polls closing. He is on track to win 47 of the state's 50 delegates.

Haley, who governed South Carolina for six years, is a capable politician. Beating her in her home state is an impressive feat. There was little doubt prior to last night, but now it's clear that Haley has no path to defeat Trump. It’s hard to envision a single state that she could win. Unless he is sentenced to prison this summer, Trump will be the Republican nominee. And, honestly, no law prohibits him from running for President from prison—an oversight, perhaps. I somewhat doubt the Republican Party would prevent him from doing so.

However, the real story is that Trump underperformed expectations and failed to expand his coalition. Once again, despite another dominant primary victory, the results highlighted Trump's vulnerabilities and offered a roadmap for defeating him in November.

Based on the exit polls, Trump’s campaign team should be popping some Xanax with the champagne over his win in South Carolina.

You cannot win the White House with the coalition that Trump is getting in these primaries. He must expand his coalition, persuade people who aren’t already on board, and get beyond the Big Lie-believing MAGA base. Through three primary contests, Trump has gained no ground.

1. Trump is Not Consolidating the Party

Winning the nomination is about garnering delegates, and on that score, Trump had a great night, but once again the results show a Republican Party divided. In New Hampshire, Trump got 55% of the vote against Haley, but that was a decidedly anti-MAGA state. Half of the voters were Independents or Democrats, and Evangelical Christians comprised only 19% of the electorate.

In South Carolina, Trump scored a few points better despite Independents making up only 21% of the electorate, while 60% were Evangelical Christians. Despite a VERY Trumpy electorate, he still lost about 40% of the vote. This is even more notable because, as NBC News Mark Murray pointed out:...