Vice President Harris is entering the race for the presidency narrowly trailing President Trump, but with an energized Democratic coalition behind her, according to new polling.

A new survey from Morning Consult found that, nationally, Ms. Harris trails Mr. Trump 45 percent to 47 percent, a result within the survey’s 3 point margin of error. The figure marks a significant improvement over President Biden’s 6 point deficit to Trump in a poll conducted by the same pollster ahead of Mr. Biden’s announcement that he would step aside.

The survey of 4,001 registered voters was conducted on July 21 and 22, after Mr. Biden’s decision to step down as the Democratic Party’s presumptive nominee.

The survey also found that 77 percent of Democratic respondents said they approved of Mr. Biden’s decision to step aside, while just 17 percent disapproved of the decision.

In terms of motivation, 45 percent of Democratic voters said they were more motivated to participate in politics this year as well as 30 percent of independents. Among Republicans 38 percent said they felt more motivated.

Among key Democratic demographics, Ms. Harris also saw significant improvements over Mr. Biden. Among Black voters, Ms. Harris leads Mr. Trump by 54 points compared to Mr. Biden, who led Mr. Trump by 39 points.

Ms. Harris also leads among voters aged 18 to 34 by 2 points whereas Mr. Biden trailed Trump by 9 points. Ms. Harris also leads Trump by 9 points among Hispanic voters where Mr. Biden led by just 4 points.

Other surveys conducted after Mr. Biden dropped out have had similar results, albeit with Ms. Harris in the lead. A Reuters Ipsos survey released Tuesday found that Ms. Harris leads Mr. Trump by 2 points, 44 percent to 42 percent.

The survey of 1,241 American adults, including 1,018 registered voters, had a margin of error of plus or minus 3 points and was conducted on July 22 and 23.

In a poll conducted by the same pollster in the beginning of July, Ms. Harris and Trump were tied in what was then a hypothetical matchup.

The survey also found that Ms. Harris assuming the position of the presumptive Democratic nominee has flipped a dynamic previously working against Democrats on its head — the issue of perceived fitness for office.

The survey found that 56 percent of respondents said Ms. Harris was “mentally sharp and able to deal with challenges” compared to 49 percent who said the same of Trump. Just 22 percent said the same of Mr. Biden.

The effects of the candidacy of attorney Robert Kennedy Jr.’s independent candidacy also shifted, according to the survey. When Mr. Kennedy was included in the race, Ms. Harris led Trump 42 percent to 38 percent, with Mr. Kennedy receiving 8 percent support.

Another survey out from Yahoo News and YouGov, conducted both before and after Mr. Biden announced he would step aside, found that Ms. Harris and Trump were tied at 46 points each.

The survey of 1,743 American adults was conducted between July 19 and 22 and had a margin of error of plus or minus 2.8 points.

The polls indicate that Ms. Harris is starting in a strong position against Trump relative to where Mr. Biden was, and the Trump campaign already is beginning to signal that the polls should not be trusted.

A memo from one of Trump’s pollsters, Tony Fabrizio, says that he expects to see what he calls a “Harris Honeymoon” over the next “couple of weeks.”

In the memo, Mr. Fabrizio says that “wall-to-wall” coverage of Ms. Harris will manifest a bump in the polls for her as she is reintroduced to voters. 

“That means we will start to see public polling — particularly national public polls — where Harris is gaining on or even leading President Trump,” Mr. Fabrizio wrote. “Due to the events of the past two weeks including our highly successful Convention, President Trump has seen a bump in his numbers in a number of recent public polls.”

Mr. Fabrizio did not name any specific polling that showed Trump enjoying a boost from the convention or the attempt on his life. 

Mr. Fabrizio added that the press would use the fact that one of the major party’s presumptive nominees has changed “as proof that the race has changed” but that “the fundamentals of the race stay the same.”