Why Montana Is a Test Case for Democrats’ Winning the Senate

BOZEMAN, Mont. — In the deeply polarized election of 2016, every state that supported President Trump backed Republican senators — and each state that Hillary Clinton carried voted for a Democratic Senate candidate.

But four years later, Democratic hopes for gaining a clear Senate majority depend in part on winning in conservative-leaning states where Mr. Trump may also prevail, even as he sags in the polls. In states like Alaska, Iowa, Georgia and here in Montana, Democrats are hoping their Senate candidates can outperform Joseph R. Biden Jr., their presumptive nominee.

That’s the dynamic Gov. Steve Bullock is counting on in Montana, where ticket-splitting is as much a way of life as fly-fishing.

Montanans have supported Republican presidential candidates, with one exception, for over a half-century. In that same period, though, they have elected a series of Democratic governors and senators. Senator Steve Daines, whom Mr. Bullock is challenging, was the first Republican elected to the Senate seat that he holds in over a century.