Baucus's approval rating with voters is underwater, with 48 percent disapproving and 45 percent approving of the job he's doing.
Former Montana Gov. Brian Schweitzer (D), who hasn't ruled out a bid, leads Baucus 54 to 35 percent in a potential primary matchup.
Baucus actually trails some other potential GOP challengers. Rep. Steve Daines (R-Mont.) leads 49 to 44 percent, and former Montana Gov. Marc Racicot (R) leads 47 to 42 percent. Baucus would have a small 3-point lead over Montana Attorney General Tim Fox at 46 to 43 percent.
If Schweitzer does run and wins the primary, the poll shows he'd fare better against all of those potential Republicans.
The automated poll of 1,011 Montana voters and 371 usual Democratic primary voters was conducted from Feb. 15-17 and had a margin of error of plus or minus 3.1 percentage points for the general election numbers and 5.1 percentage points for the primary sample.