WASHINGTON — Democratic presidential candidate Hillary Clinton has surged to a 15-point lead over reeling, gaffe-plagued Republican Donald Trump, according to a new McClatchy-Marist poll.

Clinton made strong gains with two constituencies crucial to a Republican victory — whites and men — while scoring important gains among fellow Democrats, the poll found.

Clinton not only went up, but Trump also went down. Clinton is now ahead 48 percent to 33 percent, a huge turnaround from her narrow 42-39 advantage last month.

The findings are particularly significant because the poll was taken after both political conventions ended and as Trump engaged in a war of words with the parents of Army Capt. Humayun Khan, who was killed in an explosion in Iraq 12 years ago while trying to rescue other soldiers.

“This is coming off the Democratic convention, where a bounce is expected,” said Lee Miringoff, the director of the Marist Institute for Public Opinion in New York, which conducted the nationwide survey. “What you don’t want is to have the worst week of your campaign,” a characterization many analysts use to describe Trump’s recent days.

Other polls have shown Clinton in the lead, though Marist’s is the largest so far.

Among poll respondents, Clinton was seen more often as a potential president. Fifty-three percent said they would find her acceptable; 39 percent felt that way about Trump. Francis Duffy, 76, an Upper Darby, Pa., Republican, said she was voting for Clinton because she found Trump to be scary. “I just don’t feel that Donald Trump is qualified. I think he’s a loose cannon,” she said.

CLINTON TOPS FOUR-WAY RACE

In a four-way race, Clinton retains her lead. She gets 45 percent to Trump’s 31 percent. Libertarian Gary Johnson has 10 percent, and the Green Party’s Jill Stein has 6 percent.

The new survey showed Clinton has cut sharply into the Republican nominee’s advantages in every ethnic and racial group.

After a bitter battle with rival Bernie Sanders, the independent Vermont senator whose supporters fought all the way to the convention, she has solidified her strength among Democrats, 90 percent of whom now back her, up from 83 percent last month.

Jorge Vietes, 78, a native of Argentina who lives in Stockton, Calif., sided with Sanders in the primary, and is not swayed by Trump’s efforts to woo Sanders’ voters. “I have no choice but to go for Clinton,” said Vietes, an independent voter. “Trump is kind of a crazy guy.”

Trump gets the nod from just 79 percent of Republicans, down from 85 percent last month. Some top GOP officials have put distance between themselves and the billionaire businessman, with some saying they’ll back Clinton.

Men had been the bedrock of Trump support. Last month, he was up by 14 percentage points among men; he’s now down 8.