U.S. President Barack Obama is proving to be one of Democrat Hillary Clinton's most vocal surrogates, as he mocked Republican Donald Trump on Thursday as "uniquely unqualified to be president."
"You laugh. I'm not joking, he is temperamentally unfit to be commander-in-chief," Obama told cheering Clinton supporters in Florida. It is one of two Atlantic coastal states, along with North Carolina, that both Clinton and Trump see as crucial to winning Tuesday's national presidential election.
"If we win Florida, we will win this election," Obama said in Miami, a sunny tourist mecca and home to thousands of Hispanic voters who support Clinton and are opposed to Trump's tough anti-immigration plans.
WATCH: Obama Calls Trump 'Uniquely Unqualified'
Later, Obama headed to Florida's biggest city, Jacksonville, in the northern part of the state, where Trump also campaigned Thursday.
Trump accused Clinton of "engaging in a criminal enterprise" for her handling of national security material in her emails during her four-year tenure as secretary of state.
"She's likely to be under investigation for many, many years," Trump said.
In the last dash for votes, the Republican candidate also planned rallies in the eastern state of Pennsylvania and two more in North Carolina. Trump's wife, Melania, made her first campaign appearance for her husband since the Republican National Convention in July, speaking to supporters in the suburbs of Philadelphia, Pennsylvania's biggest city.
WATCH: Trump Calls Clinton Win a 'Constitutional Crisis'
Melania Trump said if she is the country's first lady, she would be an advocate for women and children and attempt to curb bullying on social media.
"Our culture has gotten too rough and too mean," she said. "We have to find a better way to talk to each other."
Meanwhile, Clinton is also focused on North Carolina, where she is staging two campaign events.
Clinton, looking to become the country's first female president, and Trump, a blunt-spoken real estate mogul, remain locked in a tight contest five days ahead of the election. One of them will become the country's 45th president, succeeding Obama when he leaves office January 20.
Two new major national polls showed Clinton edging ahead of Trump among likely voters, with The New York Times/CBS News poll giving her a 45-to-42 percent lead and The Washington Post-ABC News tracking poll showing her with a 47-45 advantage.
The surveys included interviews with voters in the days after James Comey, the director of the Federal Bureau of Investigation, announced that the country's top law enforcement agency was taking a new look at Clinton's email practices when she was the country's top diplomat from 2009 to 2013. Investigators found thousands of emails linked to her on the computer of the estranged husband of a key Clinton aide, Huma Abedin.
In July, the FBI concluded its initial investigation of Clinton's emails, with Comey declaring that she had been "extremely careless" in dealing with national security documents but that no criminal charges were warranted. She has said on numerous occasions that her use of an unsecured private email server was a mistake, but that she did not knowingly send or receive classified material in her emails, even though investigators found such documents.
Impact of emails, video
The Times-CBS survey showed that about six in 10 voters said that neither news of the revived FBI probe nor a 2005 tape in which Trump bragged about groping women would make much difference in their vote. If anything, slightly more of those polled said Trump's behavior toward women was more of a concern to them than the controversy over Clinton's emails.
"Big picture, Clinton is still ahead," Larry Sabato, a longtime University of Virginia presidential election analyst, told CNN. "You'd still rather be Hillary Clinton than Donald Trump."
The two candidates have made numerous stops in Florida and North Carolina, two states that often flip from election to election between support for Republican or Democratic presidential candidates. State-by-state results hold the key to winning U.S. presidential elections.
The national popular vote does not determine the outcome, but rather the winner is decided in the Electoral College, with each candidate trying to amass a majority of at least 270 of the 538 electoral votes allocated according to the results in each of the 50 states and the national capital, Washington, with the most populous states carrying the most weight.
Florida, with 29, has more electoral votes than any of the battleground states where Clinton and Trump have campaigned in the waning days of the quadrennial election, while 15 are at stake in North Carolina. A collection of recent polls shows Clinton and Trump virtually tied in both states, although the most recent surveys showed Clinton edging narrowly ahead in the two states, but within the polls' margin for errors.
WATCH: What is a swing state?