Bernie's secret weapon is his strength among non-Democrats

Yet not all independents are the same: Only about half of them in New Hampshire are truly swing voters, while the rest lean strongly to one side or the other, says Liam Kerr, a co-founder of The Welcome Party, a center-left group operating in New Hampshire and South Carolina. The organization’s goal is to entice undeclared voters who typically vote only in general elections to participate in the Democratic primary.

“There are different types of independent voters, and people are speaking in different ways to them,” Kerr told me. Buttigieg and Biden are going after the traditional centrists who vote for both Democrats and Republicans depending on the election and who’s on the ballot. New Hampshire is likely to have more of these voters up for grabs this year. Undeclared voters can choose to vote in either party primary, and while they split between the ultra-competitive Democratic and Republican contests in 2016, only the Democratic primary is a real toss-up on Tuesday.

Sanders’s independent base, on the other hand, is among younger, less engaged people “who maybe are against party structures in general,” Kerr said. He needs them to show up in large numbers, and based on the modest turnout compared to expectations in the Iowa caucuses, Sanders may have cause to worry in New Hampshire. “There’s one thing we know about Sanders: He’s getting fewer votes this time than last time,” Kerr told me. “His share of independents has fallen since 2016.”