Former Vice President Joe Biden is arguably a 2020 front-runner. He has led or tied for the lead in almost every Democratic presidential primary poll he’s appeared in so far. The catch? He isn’t running — at least not yet.

How common is it for candidates to lead in the polls and never enter the race? We found 10 politicians who didn’t end up running but who, like Biden, led the field in at least one question in a national poll conducted one to two years before the New Hampshire primary (we’re about a year away from that primary now) since 1972.

Ted Kennedy is included twice, once in 1972 and again in 1976.