In three weeks, Iowa Democrats will begin the party's process for selecting a nominee to take on Donald Trump in the general election. And tonight they host a high-stakes debate. After more than a year of campaigning, it's almost time for actual voters to begin weighing in - and the race is still wide open.

Lil and Jarad Bernstein stood at the edge of the crowd gathered near the stage after a Pete Buttigieg rally in Des Moines on Sunday.

They were two of the several hundred who had turned out on a snowy evening to hear the former South Bend, Indiana mayor speak, but unlike many of the attendees - who came sporting campaign T-shirts, buttons and hats - they were not entirely sold on him yet.

"I like all of the candidates," Lil said. "I'm really just looking for someone who can win the nomination and ultimately beat Trump in the election."

"Electability" is an attribute that comes up time and time again here in Iowa and across the US. Surveys indicate that more than half of Democratic voters believe, like Lil, that the party should pick the candidate most likely to beat Trump. Winning, in their view, is the top priority. But the big question is which candidate is best positioned to do it - and why.