WASHINGTON — Democrats could get walloped in the November elections. The party gets sleepy and distracted in the midterms. And its supporters simply may not show up to vote.

Those aren’t hopeful predictions from Republicans. They’re the dire warnings of President Barack Obama, who is seeking to gin up enthusiasm for the midterm elections from party activists already looking toward the 2016 race to replace him.

The remainder of his presidency hangs on Democratic performance in the November contest. If voters hand the Senate over to Republican control, Obama will lose even the uphill chance he has to get legislation passed in his remaining time in office.

“I hope that just because I’m not on the ballot that people aren’t going to take it easy this time, because the ideas I care about and am fighting for are on the ballot,” Obama said to about 75 donors who paid $5,000 to $20,000 to hear him speak over dinner at a swanky Boston art gallery Wednesday night.

Obama’s challenge is to set an agenda for a party that is not always embracing him, especially after the problems with his health care law. There are areas of the country where he can’t campaign since he would only be a drag on more moderate Democratic candidates.

“Our message to candidates is: How can we help?” White House political director David Simas said. If showing up for a rally isn’t the answer in moderate districts, Simas said the president can give candidates a boost by raising money and setting a debate on economic opportunity.

“The president is the only individual who can really set what the national narrative is going to be,” Simas said.