"I think it is critical that Democrats unite behind one candidate for what will be a difficult and expensive race, and it's one of the reasons I have concluded that now is not the time for me to run for the United States Senate," she said in a statement released over the weekend. 

"We have good candidates like Gary Peters considering running, and a primary would be divisive at a time that cries out for unity. As someone who has spent much of my career working to bring people together, it just didn't feel right to take this step now. There may be a time when elective office is the right choice for me, but this was not it."

Peters is likely to officially announce his Senate bid soon, according to sources. On the GOP side, the most talked about candidates are Reps. Mike Rogers (R-Mich.) and Justin AmashJustin AmashOvernight Defense: Military won't lift transgender ban until Trump sends directions | House passes national security spending | Russian sanctions bill heads to Trump Overnight Finance: House passes spending bill with border wall funds | Ryan drops border tax idea | Russia sanctions bill goes to Trump's desk | Dems grill bank regulator picks House approves spending bill with funds for Trump's border wall MORE (R-Mich.), who have already been sparring.