A key metric shows that Donald Trump still has one big advantage over Ben Carson

As retired neurosurgeon Ben Carson has risen in Republican polls, the shine may have started to come off Donald Trump’s campaign.

But a new poll found that though Carson has leapfrogged Trump in Iowa, the real-estate magnate still has one key advantage.

A New York Times/CBS poll out on Tuesday showed Carson’s support among Republican voters nationwide rising to 26%, with Trump trailing at 22%. The difference was within the poll’s margin of error.

But while Carson appears to be surging, one statistic suggests that Trump’s support actually may be more durable.

As The New York Times reported, 80% of Carson’s current supporters in Tuesday’s poll said it is too early to firmly commit to voting for the retired neurosurgeon. The number of voters who said that they would commit firmly to Trump, on the other hand, is 55%.

If more of Trump’s supporters are committed to backing him in the long haul, they’re unlikely to be swayed by poor debate performances, controversies, or other scrutiny that comes with being a top-tier candidate.

Trump’s consistent lead in most of the early polls has suggested that the real-estate magnate’s rise doesn’t resemble that of a boom-and-bust fad candidate. And for his part, Trump has said that he doesn’t believe the set of recent polls that show him losing.

“I get these two polls — and remember, I don’t believe them, I don’t believe them — in Iowa. And I love Iowa,” Trump said at a campaign event on Saturday. He added on “Morning Joe” on Tuesday that he didn’t think recent polls were especially “scientific.”

After spending months touting his strong poll numbers in public events and media appearances, a slew of new polls have found Trump trailing Carson in Iowa, the crucial first-nominating state.

Two polls last week gave Carson his first lead ever in Iowa. And Loras College and Monmouth University polls out Monday found Carson pulling into first place in the Hawkeye state — and leading by double digits.

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