New polling suggests Vice President Harris is maintaining her statistical tie with President Trump in the 2024 election, thanks, in part, to enthusiasm from Democrats who previously had placed little hope in President Biden. Independent candidate Robert F. Kennedy Jr. has seen his support dwindle nationally during Ms. Harris’s rise. 

The new survey from the University of Massachusetts at Amherst finds that Ms. Harris leads Trump by three points nationally, 43 percent to 40 percent. Mr. Kennedy takes 5 percent of the vote nationally in the survey. 

The poll was conducted shortly after Ms. Harris launched her campaign, between July 29 and August 1 with 1,000 respondents. The margin of error is 3.8 percent. 

In the same UMass poll from January, Trump lead Mr. Biden by four points, outside of the margin of error. Mr. Kennedy took 9 percent of the vote nationally in that survey just more than six months ago. 

The architects of the UMass poll say Ms. Harris’s sudden rise likely contributed to greater Democratic enthusiasm for the election. 

“Harris’s entry has really shaken up the presidential race,” says a professor of political science at UMass Amherst and co-director of the poll, Jesse Rhodes. “Where Donald Trump was once heavily favored over Joe Biden, we now see Harris with a narrow lead,” Mr. Rhodes adds, attributing the rise to excitement among young, Black, and Hispanic voters.

Compared to Mr. Biden in the January poll, Ms. Harris has gained 11 points among Democrats, 17 points among independents, 12 points among self-described moderates, 13 points among Hispanics, and 14 points among voters under the age of 30. 

When voters who are planning to vote for Ms. Harris were asked by pollsters why they are voting against Trump, their top two reasons for doing so was because “He is a threat to America” and “He was responsible for the January 6th insurrection.” Among Trump supporters, they say their top two reasons for supporting the former president were because of his “first term accomplishments” and he “will save America.”

Supporters of Ms. Harris say their most important reasons for voting for her are because she brings generational change to the White House and that she will “strengthen America’s global standing.” Those who are voting against her list Biden administration policies and the fact she would “weaken” America’s standing as the two greatest reasons for voting against her. 

On the issues, Ms. Harris has an advantage on some domestic priorities like abortion rights, green energy investments, healthcare affordability, and education. Trump holds just a six-point lead over Ms. Harris on the issue of who will better handle crime. He holds the same margin lead over Ms. Harris on the economy. 

On personal characteristics, voters view Ms. Harris as more moderate, compassionate, likable, and intelligent. Trump is viewed as being stronger, more patriotic, and more experienced. 

Nearly every poll in recent days has show Ms. Harris and Trump in a statistical tie. On Monday, Trump’s pollsters’ firm, Fabrizio Lee, in a memo first obtained by Politico, said the two candidates were tied nationally both in a head-to-head race, and with Mr. Kennedy in a three-person contest. Ms. Harris and Trump are tied at 48 percent each in the head-to-head, and they both take 45 percent when Mr. Kennedy, who takes just 4 percent, is included.