Rep. Denny Rehberg (R-Mont.) will announce Saturday he is challenging Sen. Jon Tester (D-Mont.).
"It's happening Saturday," said a knowledgeable Montana GOP political operative. "He's running. There is a lot of support and enthusiasm back home, and Denny knows he can win."
And some internal polling, including a weird three-way matchup:
The operative offered some internal Rehberg polling numbers showing the Montana Republican in a statistical tie with Tester in a prospective 2012 matchup.
The Opinion Diagnostics survey of 400 likely Montana voters showed 49 percent backing Rehberg compared with 43 percent for Tester and 8 percent undecided. In a three-way matchup featuring Democratic Gov. Brian Schweitzer running as an independent, Rehberg led 44 percent to Tester's 28 percent and Schweitzer's 18 percent. Eleven percent were undecided.
The poll, conducted Jan. 5, has a margin of error of 4.65 percent.
SSP is on the verge of publishing our senate race ratings, and internally, we'd already agreed that MT-Sen was a Tossup prior to this announcement. This news confirms our view that this race will definitely start life as a Tossup.