Daines raised approximately $415,000 in the last three months, according to a source close to the campaign who said it "demonstrates Daines's growing consideration of this race."

That's a jump from the $250,000 he raised in the first three months of the year.

The first-term congressman is seriously mulling a run for the seat held by retiring Sen. Max BaucusMax Sieben BaucusGreen Party puts Dem seat at risk in Montana Business groups worried about Trump's China tariffs plan Farmers hit Trump on trade in new ad MORE (D-Mont.), and is the GOP's most likely top-tier candidate. Democrats are hoping that former Montana Gov. Brian Schweitzer (D) will jump in on their side. Recent polls show a tight race if the two face off.