A new Montana Senate poll offered fresh evidence that Sen. Jon Tester will have trouble holding his seat against Republican Rep. Denny Rehberg.

The two state political powerhouses were statistically tied in a new survey by Mason-Dixon Polling and Research, which was conducted for Lee Newspapers with 20 months to go in the race.

The Democratic Senator took 46 percent and Rehberg 45 percent, and 9 percent were undecided. The poll of 625 registered voters was taken March 14-16 and had a 4-point margin of error. Still, a 12-point lead among independents offered encouraging news for the incumbent.

“It’s one of the few races you’ll see where both candidates already have a built-in statewide organization,” Mason-Dixon President Brad Coker said.

Tester is among national Republicans’ top targets, and Rehberg’s candidacy gave the GOP a top challenger.