Trump’s showing among all college-educated South Carolina voters fell between his performance in Iowa (22 percent) and New Hampshire (where he carried a 30 percent plurality). Comparing his showing among college- to non-college voters, Trump has now run five points weaker in Iowa, 12 in New Hampshire and fully 17 in South Carolina. And though the margins have been thin, Rubio has now carried the most college-educated Republicans in two of the first three contests.

If Trump does face a ceiling in the race, it is likely constructed from the relatively greater resistance he is confronting among these white-collar largely suburban and often professional Republicans—who provided critical support for the past two nominees, John McCain in 2008 and Mitt Romney in 2012. In polls these voters have been somewhat less likely to support Trump’s signature proposals to deport undocumented immigrants and temporarily ban Muslims from entering the U.S.; perhaps more significant, those white-collar Republicans have also been more likely to question whether Trump has the personality, skills and above all temperament to succeed as president. As Jane Kizer, a computer programmer, told me while waiting to enter a conservative rally in Greenville last week: “He says what needs to be said, and what a lot of people are thinking. Now a lot of people are saying, ‘It’s been said, and we need a leader.’”

But after the first three contests, it’s an open question whether any of Trump’s remaining rivals can consolidate enough of the voters still skeptical of him to overtake him, particularly given his dominant position with the party’s blue-collar wing.

So far, Cruz’s coalition has been too narrow to threaten Trump. Throughout the first three contests, Cruz has been lopsidedly dependent on evangelical Christian voters—and even that foundation cracked on him in South Carolina.

In Iowa, Cruz won 34 percent of voters who identified as evangelicals but only 18 percent of those who did not. In New Hampshire, Cruz won 23 percent of evangelicals, but just eight percent of those who did not identify with that faith tradition. In South Carolina, Cruz carried 27 percent of those who identified as evangelicals and only 13 percent of those who did not.

Across all three states, Cruz’ performance among voters who were not evangelicals varied little from the meager showings by Rick Santorum (in 2012) and Mike Huckabee (in 2008), two previous evangelical favorites who failed to expand from that faction sufficiently. Relative to Santorum and Huckabee, Cruz was supposed to be better positioned to add economic and national-security conservatives to his evangelical base. But so far, Cruz hasn’t broadened more effectively than they did.

Viewed through the ideological lens, Cruz’ support is just as narrow: Although last night he carried a 35-percent plurality of voters who identified as very conservative, he attracted just 17 percent of somewhat conservative voters and 7 percent of moderates. In Iowa and New Hampshire, Cruz also won at least twice as much support from “very” as “somewhat” conservative voters; his support among moderates has not cracked double-digits in any of the three states.