One way to know that Donald Trump isn’t just a flash in the pan doomed to go the way of Herman Cain and Michele Bachmann is to look at who Republican voters think will win the nomination. It’s one thing for a candidate to lead the field. It’s another to convince the primary electorate that he’ll continue leading the field all the way until the end.

Trump has managed to do just that:

A majority of Republican voters believe that Donald Trump will be their party’s presidential nominee, according to a Rasmussen poll released Friday.

The poll found that 57 percent of Republican voters think Trump is likely to win the nomination, up from 27 percent two months ago, when the billionaire businessman officially launched his campaign. Only 15 percent of Republican voters see a Trump nomination as “not at all likely,” down from 29 percent over the same span.

Among all voters, 49 percent believe Trump will be the Republican candidate for president, up from 23 percent. Voter confidence in Trump may be a reflection of national polls that have the businessman up by double-digits in the Republican primary.

Pervasive beliefs among the electorate can become self-fulfilling prophecies. Little over a month ago Trump was still seen as a joke candidate in many quarters, one who might even lead the polls for a little while but who few people believed would actually win. As an outsider candidate, making people believe you can actually win is often the hardest part. It remains perhaps Bernie Sanders’ greatest challenge.

Among the GOP primary electorate, Trump has already cleared that hurdle. Establishment Republicans have a lot of work to do if they want to knock him off his perch.

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Follow David on Twitter @DavidOAtkins. David Atkins is a writer, activist and research professional living in Santa Barbara. He is a contributor to the Washington Monthly's Political Animal and president of The Pollux Group, a qualitative research firm.