Incumbent Lisa Murkowski has a dominant fundraising advantage over challenger Kelly Tshibaka in the U.S. Senate race. In the race for U.S. House, Nick Begich enjoys a big cash-on-hand advantage despite raising the least of the three main contenders in the race, according to the most recent Federal Election Commission reports.

A total of about $4 million was raised on Murkowski’s behalf by her campaign ($1.6 million) and the political action committee Alaskans for LISA ($2.4 million) during the three-month quarter ending June 30. The 20-year Republican incumbent had $6.1 million in her cam...