CLEVELAND — Hillary Clinton and Donald J. Trump immersed themselves in on-the-ground campaigning on Monday, bearing down on Ohio and sending surrogates to other swing states as the campaign turned to its final phase.
With Mrs. Clinton moving from a summer of fund-raising back to retail campaigning, she and Mr. Trump crossed paths in Ohio, with their motorcades all but passing each other and the planes of the candidates and their running mates ending up on the tarmac of Cleveland Hopkins International Airport at the same time.
While Mrs. Clinton holds comfortable leads in many swing-state polls, she worked on Monday to confront nagging doubts about her candidacy. She let the press corps onto her campaign plane for the first time this election cycle and met with them briefly to say hello; she gathered with union leaders in Cleveland while her husband, Bill Clinton, appeared at a Labor Day parade in Detroit; and she enlisted the help of her primary opponent, Senator Bernie Sanders, who made his first solo appearance on Mrs. Clinton’s behalf in an effort to draw out his supporters in New Hampshire.
Not to be outdone by Mrs. Clinton’s outreach to the news media, Mr. Trump invited reporters onto his personal plane, where he sought to clarify his views on immigration. He said he opposed any path to citizenship for the 11 million immigrants in the country illegally, but did not explicitly rule out a long-term path to legal status if the nation’s immigration system is overhauled.
“We’re going to make that decision into the future,” Mr. Trump said. But, he added, “to become a citizen, you are going to have to go out and come back in through the process. You’re going to have to go out and get in line. This isn’t touchback. You have to get in line.”
On the plane, Mr. Trump also told reporters that, “as of this moment,” he planned to attend all three debates, saying that only a “natural disaster” could make him change his mind. He added that, while he was preparing, he was not holding any mock debate sessions.
Labor Day has traditionally been the beginning of a two-month sprint to Election Day, in which candidates try to seize voters’ attention as summer fades and debates loom. Monday proved no exception. At one point, all four presidential planes — one each for Mr. Trump and his running mate, Gov. Mike Pence of Indiana, and Mrs. Clinton and her No. 2, Senator Tim Kaine of Virginia — idled on the tarmac at Cleveland Hopkins International Airport, highlighting the importance of a state that Republicans believe Mr. Trump must win to have any chance of reaching the White House.
“Labor Day comes, and it’s kind of like a recalibration,” said Beth Myers, who managed Mitt Romney’s 2008 presidential campaign and served as his senior adviser in 2012. “You see the finish line, you see that there’s not too many game-changing events left, and most campaigns take a measure of where you are on Labor Day.”
This cycle, however, both candidates have eschewed traditional campaigning, albeit in divergent ways. Normally, they would already have been circling each other in swing states as autumn approaches.
But Mrs. Clinton has spent most of the summer away from the campaign trail, focusing on fund-raising in places like the Hamptons and Beverly Hills with celebrities like Jimmy Buffett and Harvey Weinstein. Mr. Trump has also kept a languid pace, favoring large rallies, often in the evening, over several daily campaign stops.
This year’s Labor Day campaigning reflects another difference. The conventions fell earlier in the summer than usual, leaving five weeks between the end of the Democratic National Convention and the holiday weekend.
Mr. Trump, a political novice, and Mrs. Clinton, a veteran politician, face the challenge of confronting historically low approval ratings among voters for whom they are well-known commodities.
“Labor Day used to be this big, important marker in the campaign season,” said Amy Walter, national editor at the nonpartisan Cook Political Report. “A kickoff, if you will. Today, it feels like the start of the third quarter instead of the kickoff.”
“The candidates are well-defined, the ads have been running for months and TVs have been saturated with talking heads,” she added.
Mr. Trump tried to burnish his image as a statesman last week with a hastily arranged trip to Mexico City. He has also tried to increase his outreach to minorities, from a promised “softening” on immigration that concluded with a fiery, nativist speech in Phoenix, to a stop at a black church in Detroit.
At a diner on Monday in Cleveland, Mr. Trump met Maria Hernandez, a Mexican-American who said she was supporting him. “Mexican-American supports Trump,” he said. “It’s so nice.” Then he turned to the nearby reporters to emphasize his focus group of one: “Make a note of it, guys,” he said.
Earlier, speaking to a dozen white men and a lone white woman at an American Legion post here, Mr. Trump criticized China’s treatment of President Obama: When the president landed in Hangzhou for the Group of 20 summit meeting, the host country forced him to disembark from the plane’s belly. Mr. Trump said he would not have gotten off the plane, instead saying, “Let’s get the hell out of here.”
He also took a shot at Mrs. Clinton, saying, “And she looks presidential, fellows?”
Mrs. Clinton dived back into campaigning by appearing with Mr. Kaine at a Labor Day festival here. She was joined by labor leaders, including the A.F.L.-C.I.O.’s president, Richard L. Trumka; Lee Saunders, the president of the American Federation of State, County and Municipal Employees; and Randi Weingarten, the president of the American Federation of Teachers, one of the first unions to endorse Mrs. Clinton last year.
Labor leaders overwhelmingly supported Mrs. Clinton over Mr. Sanders during the Democratic primaries, though many rank-and-file union members were drawn to Mr. Sanders’s promise to take on income inequality. Mrs. Clinton has consistently promised to strengthen labor unions as part of her overall plan to lift wages.
Mrs. Clinton’s surrogates were also out in force. On a sunny morning in Pittsburgh, Mr. Kaine and the man he hopes to succeed, Vice President Joseph R. Biden Jr., spoke at an outdoor rally before the city’s Labor Day parade, addressing a crowd that included many people in union T-shirts. Mr. Kaine assailed Mr. Trump for refusing to release his tax returns, then turned the stage over to Mr. Biden.
“My name is Joe Biden, and I work for Hillary Clinton and whatever the hell this guy’s name is,” he said.
Mr. Biden then portrayed Mr. Trump as out of touch with families struggling financially. “He really does believe that workers make too much,” Mr. Biden said. “He really does believe that the problem is American workers are lazy.”
Mr. Sanders planned to campaign for Mrs. Clinton later on Monday at a rally in Lebanon, N.H.
