"I was thrilled when Gary announced that he would be running for the U.S. Senate because he's exactly who we need standing up for us," Granholm writes in a fundraising email to Peters's supporters.  "Gary's record in the U.S. House of Representatives has been about one thing and one thing only – fighting for middle class families no matter the stakes. Whether it meant taking on special interests to advocate for Michigan manufacturers or stop restrictions to women's health care, Gary has proven to us that he is the kind of progressive champion we need in Washington."

Michigan Democrats have rallied around Peters as their candidate in the Democratic-leaning state. Former Michigan Secretary of State Terri Lynn Land (R) is the only GOP nominee in the race at this point after a number of other Republicans chose not to run.