In the past few days, Obama has issued stark warnings to Democrats that they could lose. According to several Obama aides and outside advisers, the change in tone is, in part, an inevitable product of the approaching election day. But it also is an acknowledgment of some of Clinton’s weaknesses.
White House officials have privately fretted about some of Clinton’s recent missteps, said supporters of the president who spoke on the condition of anonymity to discuss the issue frankly. Those mistakes and the narrowing polls have only intensified the president’s focus on the campaign, these officials said…

In a recent conference call with Clinton donors, former White House senior adviser David Plouffe told her supporters that it was imperative that Democrats win a decisive victory in November to prevent another politician like Trump from emerging on the national stage, according to one participant…

But there are limits to what he can do for his former secretary of state. “He understands at the end of the day, Hillary Clinton is the one who has to give voters, and particularly the voters who elected him in 2008 and 2012, a reason to vote for” her, said one Obama confidant. “He knows he can’t deliver the election, and I don’t think the campaign is asking that. But he can help.”