Mr. Martin is a party insider who knows his way around the D.N.C.

He has led his state party since 2011 and is a vice chairman of the national party. He also leads the Association of State Democratic Committees, a body that lobbies for state parties within the national committee — and a power center that has irritated other D.N.C. officials, but one that his allies see as a sign of his strengths.

“He has built power within the D.N.C. by building relationships with state party chairs,” said Senator Tina Smith, a Minnesota Democrat. “What that demonstrates is that he is going to trust people who are closest to the ground, closest to the voters, closest to the work.”

Senator Amy Klobuchar of Minnesota said Mr. Martin’s focus on state parties showed his interest in competing everywhere.

“What he will do nationally is focus on keeping our blue states strong, but also making sure our purple states — which, of course, didn’t happen last time — go blue and the red states go purple,” she said. “That’s part of what he’s been doing with talking about building up these state parties and making sure we’re hitting every area.”