For two months as he campaigned for Democratic National Committee chair, Ken Martin worked methodically through a call sheet of the committee’s 448 members, sometimes on the phone for as long as an hour,

The Democratic National Committee chose Mr. Martin, the leader of the Minnesota Democrats, to help oversee a demoralized national party split over its future and its response to President Trump.

Democrats on Saturday elected Ken Martin, the party leader in Minnesota, as the national chair, turning to a low-profile Midwestern political operative to coordinate their resistance to Donald Trump’s presidency.