In a head-to-head matchup, Trump leads Clinton by a margin of 42 percent to 39 percent in Florida, erasing the Democrat's eight-point lead in June, according to the poll conducted by Quinnipiac University. Trump also leads by a margin of 41 percent to 36 percent when Libertarian candidate Gary Johnson and Green Party candidate Jill Stein are added to the mix.
Peter A. Brown, assistant director of the Quinnipiac University Poll, said one factor could be the recent controversy surrounding Clinton's use of a private email server and handling of classified information while she served as secretary of state. The Department of Justice decided against prosecuting Clinton, but FBI Director James Comey publicly criticized her for being "extremely careless."
"While there is no definite link between Clinton's drop in Florida and the U.S. Justice Department decision not to prosecute her for her handling of e-mails, she has lost ground to Trump on questions which measure moral standards and honesty," Brown said in comments accompanying the poll results.
Trump's lead in the head-to-head matchup is within the poll's 3.1 percentage-point margin of error.
Clinton led in Florida by a margin of 47 percent to 39 percent in a Quinnipiac poll released June 21. One of the biggest shifts in the new survey involves independent voters, who favored Clinton by nine percentage points in the June poll. The poll released Wednesday indicated that Trump leads among independents by a margin of 43 percent to 30 percent.
Overall, however, the new poll again reflected deep divisions among voters based on race, gender and age. Trump dominates among white voters, men and older Floridians. Clinton holds big leads among non-white voters, women and younger people.
Brown said Trump, who has angered many Hispanics with his stances on immigration issues, could have a difficult time winning in the diverse state if he does not improve his numbers among non-white voters.
"In Florida, Donald Trump is getting only 21 percent of the non-white vote," Brown said. "Although he is winning among white voters, who are mainly Republican, victory in Florida will be a very difficult lift for him if he can't do better among non-white voters."
Nevertheless, the poll indicates Trump has momentum as Republicans prepare to gather next week in Cleveland for the GOP national convention. Quinnipiac also released poll results Wednesday showing the candidates tied in Ohio and Trump leading by two points in Pennsylvania, both of which also are closely watched swing states.
"Donald Trump enters the Republican convention on a small roll in the three most important swing states in the country," Brown said. "He has wiped out Hillary Clinton's lead in Florida; is on the upside of too-close to call races in Florida and Pennsylvania and is locked in a dead heat in Ohio."
The Connecticut-based Quinnipiac frequently conducts polls in Florida and other states. In the latest poll, it surveyed 1,015 registered Florida voters from June 30 to Monday.
In a major shift from last month, a poll released Wednesday shows Republican presidential candidate Donald Trump overtaking Democrat Hillary Clinton in the key swing state of Florida.