BILLINGS, Mont. (AP) — The two candidates vying for a Montana U.S. Senate seat that's considered pivotal in determining if Democrats can wrest the majority from Republicans come November are set to face off in a Monday night debate.

First-term Republican Sen. Steve Daines is leaning on the popularity of President Donald Trump as he seeks to fend off a strong challenge from Democratic Gov. Steve Bullock.

Their face-to-face meeting in Missoula comes as the national political scene has been roiled by a Supreme Court vacancy, revelations about Trump's taxes and the government's faltering efforts to contain the pandemic amid economic havoc.

Bullock is barred by term limits from seeking a third term in the governor's mansion. Before entering the race he dropped out of the Democratic presidential primary after attracting little support in a crowded field.

He's criticized an absence of federal leadership on the coronavirus pandemic. Daines has defended the president and sought to shift blame to China, where the virus originated.

The debate is scheduled to be broadcast live at 7 p.m. Mountain time on Montana PBS.

Most counties are conducting elections by mail and must send out ballots to registered voters by Oct. 9.

Absentee ballots for in-person voting are available Oct. 5 in counties conducting polling place elections.