Russell Berman writes:

If Senator Bernie Sanders wins the Democratic primary in New Hampshire on Tuesday, it’ll likely be thanks to voters who are—like him—not actually Democrats.

The Vermont senator’s lead in several public polls is bolstered by his strong support among independent, or undeclared, voters, who are welcome to participate in New Hampshire’s primary and could make up as much as 40 percent of the electorate.

Beyond New Hampshire, Sanders’s advantage among independent voters could be his secret weapon in the many large, delegate-rich states that allow them to cast ballots in the Democratic primary. Four years ago, he crushed Hillary Clinton among non-Democrats, according to exit polls; in New Hampshire, he won nearly three-quarters of them, which made up the bulk of his 20-point margin of victory.

Generally, candidates care less about who is backing them as long as they’re winning. But the source of Sanders’s strength could both help and hinder his candidacy if the primary turns into a delegate-by-delegate battle heading into the Democratic National Convention in July. The states that hold either partially or fully open primaries include some of the largest in the country—California, Texas, Ohio, Illinois, Virginia, and Massachusetts.

To the Sanders campaign, his support among non-Democrats is an argument in favor of his electability: Only he can excite the younger, less politically engaged cohort of people who aren’t registered with either party and might otherwise stay home or vote for a third-party contender in November. But the same dynamic could resurrect old resentments within the Democratic establishment that a candidate who for decades has refused to run on the party’s banner in Vermont is poised to capture its presidential nomination. [Continue reading…]