Ted Cruz has an increasingly serious demographic problem.

More than 8 of 10 Cruz supporters in South Carolina considered themselves to be evangelical Christians, according to preliminary exit polls.

His candidacy depends almost exclusively on evangelicals. Among non-evangelicals, he won 13 percent of the South Carolina vote. That puts him behind Donald Trump, Marco Rubio *and* John Kasich.

South Carolina seemed a natural target for Cruz after he rode a wave of evangelical support past Trump to win the Iowa caucuses two weeks ago. The voters in South Carolina were exactly the type that Cruz has courted; preliminary exit polling showed 72 percent of voters there were evangelical. Compare that with Iowa, where 64 percent of caucusgoers were evangelical, and you might expect Cruz to win South Carolina handily.

Yet, in contrast to Iowa, where Cruz outpaced Trump by double digits among evangelicals — 34 percent to 22 percent — Trump got more of the evangelical vote than Cruz in South Carolina: 33-27. Cruz's shared of the evangelical vote only modestly outpaced Rubio (22 percent), who edged out Cruz for second place overall.

There’s only so much to go around, and if Trump continues taking a third of it and Rubio is competing too, Cruz’s entire path to victory becomes much more tenuous than it previously seemed.

We previously wrote about how the next few weeks of the calendar could be very good for Cruz if is he continued to win evangelicals by margins like the one he did in Iowa.

That's because the Republican primary calendar is frontloaded with several of the nation’s most evangelical states. And these states are worth a lot of delegates. But if Cruz loses his most crucial demographic to Trump in these upcoming states, it turns that advantage on its head.

Were Trump not a factor, Cruz would be the favorite in many of these evangelical states. But with Trump in the race, each evangelical state does much less for Cruz than it otherwise might have. Even if Trump eventually does fall – a notion that seems less and less likely every day – most of the very evangelical states would likely have already voted.

Beyond Super Tuesday, Cruz doesn’t have many more favorable states to look forward to. And with Trump in the race, he’ll have to settle with splitting the crucial evangelical vote.