Donald Trump has led Republican primary polls for six months now. Still, many have wondered whether his supporters will actually stick with him in the end — or whether they'll get cold feet and opt for a more conventional choice when the time comes to vote.

But a new NBC News/SurveyMonkey national poll found that Trump supporters were more likely to say they were "absolutely certain" about their choice than Cruz or Rubio supporters were.

The poll, which was conducted online, found Trump in first place with 35 percent nationally, Cruz in second with 18 percent, and Rubio in third with 13 percent. It followed up with those voters by asking just how set they were on that choice, and here's what the results were:

Fifty-one percent of Trump-supporting respondents say they're "absolutely certain" they will vote for Trump. That still, of course, leaves about half who think they might change their minds. But Trump's "absolutely certain" number is higher than Cruz's (36 percent) and Rubio's (just 26 percent).

Now, don't completely take this at face value. This is just what those poll respondents are saying — they could behave differently at crunch time. And since Trump has gotten far more media coverage than Cruz or Rubio, it's understandable that more of his supporters would feel they've had enough information to make up their minds.

Still, it can't be good news for Rubio that of his relatively meager 13 percent support among Republicans, a mere quarter say they're certain they'll vote for him. Head over to NBC News for more, or read the full poll results here.