He just replaced his campaign manager. It's one of the warning signs:
With Michigan looming as a now key Senate race, Democratic Rep. Gary Peters, who is locked in a tight battle with Republican Terri Lynn Land, has replaced his campaign manager.
Paul Tencher, who ran now-Sen. Joe Donnelly’s winning campaign for the Democrats in Indiana last cycle, will take over as the head of Peters’ campaign operation. Tencher will replace Julie Petrick, who is stepping aside for personal reasons, Peters said in a statement.
"Personal reasons" is DC-speak for "can't handle the pressure of a suddenly-tougher campaign." This does not mean that Gary Peters will lose the election... but it has become increasingly clear over the last month or so that Peters is not actually winning this election, either. This is undoubtedly worrying national Democrats, since if Michigan collapses then the question stops being 'will the GOP win the Senate in 2014' and starts being 'will the GOP keep the Senate in 2016.' Hence... the shakeup.
Moe Lane (crosspost)
PS: Terri Lynn Land is indeed the GOP frontrunner at this point, and the expected nominee.