Unlikely as it may seem, Democrats consider tiny tribal villages like this one — about 60 miles upriver from the Bering Sea, with a population a little over 400 — so vital to their tenuous majority in the United States Senate that they are building a vast outreach operation here and across rural Alaska. Native populations are one of the most important but least understood constituencies for the Democratic Party, and as Alaska has shown, they do not predictably break for one party or the other.

Six years ago, their support made all the difference for Senator Mark Begich, a Democrat who persuaded the tribes to vote for him over Ted Stevens. Mr. Stevens, the incumbent, was a towering figure among Alaska Natives until his legal troubles proved too much to overcome.

This year, Democrats are redoubling their outreach, knowing that just a few votes in a few small villages could tip the balance of Mr. Begich’s re-election bid, and possibly the entire Senate. The effort, like a similar one aimed at Native Americans in Montana, will involve 130 workers in five new field offices spread out across a land mass roughly twice the size of Texas — from here in the state’s southwest to north of the Arctic Circle.

...

Beyond Alaska, Democrats are hitting the ground again in Montana, where Native Americans make up 6.5 percent of the voting-age population, or 50,000 people. A good response there could help improve Senator John Walsh’s tough odds in turning his temporary Senate appointment this year into a full term. (He replaced Max Baucus, who is now the ambassador to China.) Democrats plan to have field offices on or near all seven of Montana’s reservations. The week after Mr. Walsh was sworn in, he visited six of those reservations.