But Democratic sources said the amount of opposition research on the former governor painted a grim picture. A report in the Great Falls Tribune tomorrow will outline Schweitzer’s ties with a dark money organization, which may have been deeper than Schweitzer had let on.

And Montana elected officials won’t shed many tears over Schweitzer’s decision. He and Baucus have had a strained relationship for years; Schweitzer allowed speculation that he might challenge Baucus in a primary to swirl, though he never truly considered running against the state’s senior senator. And though Schweitzer worked closely with Sen. Jon Tester when Tester was in the Montana legislature, Tester felt Schweitzer had a penchant for taking credit for accomplishments that should have been shared. Tester made several eyebrow-raising comments in a Politico report earlier this week highlighting Democrats’ complicated feelings about the former governor…

Without Schweitzer in the race, Daines would be the favorite to pick up a seat for Republicans, who likely will need to win a net of six seats in November 2014 to win control of the upper chamber. Republicans are likely to win Democratic seats in South Dakota and West Virginia, and vulnerable Democratic incumbents in Arkansas, Louisiana, North Carolina and Alaska will face tough fights to win new terms. Adding Montana to the list of competitive seats only improves the GOP’s chances of winning control.