Colorado Sen. Michael Bennet distributed a fundraising solicitation Wednesday on behalf of his Democratic colleague to the north, Montana Sen. Jon Tester.

Tester is up for re-election in 2012 and facing a top-tier challenger in Rep. Denny Rehberg (R). Bennet survived his own election battle last year, winning a full term after being appointed to the Senate two years earlier.

“I saw first-hand in 2010 what DC special interests can do when they go on the attack — and I was able to withstand those attacks because supporters like you had my back,” Bennet wrote in the fundraising email. “Now let’s get Jon’s.”

Tester had $562,000 in the bank at the start of 2011. Rehberg was close behind with $553,000. Both candidates want to have a strong fundraising quarter to build momentum for the rest of the cycle.

Bennet’s email was part of a Tester effort to raise another $50,000 by next Thursday’s first-quarter deadline.

“I need allies like Jon, and that’s why I need allies like you to stand with him in his tough reelection campaign,” Bennet wrote. “National Republicans know the road to expanding their power in the Senate runs through the West, and they’ve zeroed in on Montana.”