Democrats are increasingly worried about Sleepy Joe Biden’s string of stumbles on the campaign trail and shaky debate performances.

CNN’s Ana Cabrera: “President Obama reportedly told Joe Biden directly, quote, ‘you don’t have to do this, Joe, you really don’t.’” (August 17)

Democrat: Kirsten Powers: “I think Biden looked unsteady at many points. … he looked kind of unsteady and almost deer in the headlights.” (September 12)

NBC’s Mike Memoli: “He’s not the most polished speaker anymore, I think, that, no one would deny.” (September 12)

CNN’s Jake Tapper: “A Senior Obama-Biden Administration official told me, quote, ‘Biden’s strength has never been his clarity of message or his delivery. But watching his long, winding answers that don’t really make sense in recent debates has also raised the question as to whether that has gotten worse and whether he is up for this.’ This is your frontrunner.” (September 15)

Democrat U.S. Senator Cory Booker: “There’s a lot of people who are concerned about Joe Biden’s ability to carry the ball all the way across the end line without fumbling. … There are definitely moments when you listen to Joe Biden and you just wonder.” (September 12)

CNN’s Ron Brownstein: “He’s not that good at this. He’s clearly not that strong a candidate thinking on his feet” (September 13)

The Wall Street Journal’s Sabrina Siddiqui: “I think there are some concerns. And they’ve been expressed by Democrats themselves, over whether Joe Biden is equipped to withstand a very grueling campaign.” (September 13)

Huffington Post’s Arthur Delaney: “Joe Biden was really shaky both because he was stumbling through his answers and also because the substance of those answers hasn’t really gotten better” (September 13)

Associated Press’ Jonathan Lemire: “I think we’re going to see growing questions … wondering if he has the mental and physical stamina to get through this campaign” (September 13)

CNN’s Ana Cabrera: “So tell me what you make of this New York Times piece that cites a source as saying Obama actively tried to discourage Biden from running this time and that Obama warned Biden’s aides to make sure Biden didn’t embarrass himself or damage his legacy by running for president.” (August 17)

Associated Press’ Julie Pace: “[There is a] real conversation that is happening among Democrats … Has he lost a step? Is he too shaky? That is an actual conversation that is happening.” (September 13)