A burst of ad spending is part of a campaign tactic in which the major parties try to boost fringe hopefuls on the other side.

Dan Sullivan, a retired schoolteacher from tiny Petersburg, Alaska, shares a name with the incumbent senator he hopes to defeat. Is he a spoiler trying to divide the Republican vote? We traveled to Alaska to find out.

© Christopher Miller for The New York Times

Ms. Peltola, the Democratic Senate candidate, fired a longtime senior aide and named a new campaign manager.

© Kerry Tasker/Reuters

The campaign of Mary Peltola said it was focused on issues important to Alaska and did not approve a message of support from Ms. Harris.

© Kerry Tasker/Reuters; Philip Cheung for The New York Times