WASHINGTON (AP) — Their rivals are busy answering voters' questions at town halls across South Carolina, glad-handing with business owners in New Hampshire and grinding to hit every one of Iowa's 99 counties.

But the front-runners for their party's nomination, former President Donald Trump and President Joe Biden, are barely campaigning in crucial early-voting states as the primary season enters the fall rush.

Biden is attending a union parade in Philadelphia on Monday. But he has held just one campaign rally in the four-plus months since he formally launched his 2024 reelection bid. Trump, who complained of his Biden's “basement strategy” in 2020, has not campaigned for three weeks now, last appearing at the Iowa State Fair on Aug. 12.

The schedules underscore the reality that Democrat Biden and Republican Trump, despite underwater approval ratings nationally, are the dominant front-runners. Biden faces only token opposition in anti-vaccine activist Robert F. Kennedy Jr., who is viewed more favorably by Republicans than Democrats, while Trump is currently beating his closest rival by large margins, according to recent polls.

“When you have a massive lead over your primary opponents, it doesn’t seem like a lot of point,” said veteran Republican pollster Whit Ayres, speaking about the early-state campaigning typical at this stage of a race.

Biden and Trump have worked to project an air of inevitability four months before voting begins in 2024. Biden has focused on governing and traveling the country to promote his policy accomplishments. Trump repeatedly skips events with other candidates and passed on the first Republican primary debate last month.

But both have different reasons for their relative absence from campaigning.

Trump's team has been consumed by the criminal charges he now faces in four separate jurisdictions accusing him of illegally trying to overturn the results of the 2020 election, improperly classifying hush money payments in business records, mishandling classified documents after leaving office and trying to obstruct that investigation.

Trump has complained that the looming trials will force from campaigning.

"I’m sorry, I won’t be able to go to Iowa today, I won’t be able to go to New Hampshire today because I’m sitting in a courtroom on bull——,” he said during his last visit to New Hampshire, in August.

For now, Trump's bookings and arraignments have actually served as his highest-profile campaign events.

His trips to jails and courthouses in New York, Miami, Washington and Atlanta have dominated coverage of the race, with his movements tracked by news helicopters and broadcast live on television and across the internet. His historic mug shot, now featured on T-shirts, mugs and posters, helped his campaign raise more than $20 million in August alone.

Aides say his schedule will ramp up after the Labor Day weekend, with trips this coming week to Iowa and South Dakota — neither is a key primary or general election state — and California after that. He has also been busy behind the scenes. Beyond golfing and meetings with his lawyers, Trump has called into conservative podcasts, taped videos he releases on his Truth Social network and attended fundraisers, both at his New Jersey club and in other states.

Last month, he traveled to Nashville, Tennessee, for a fundraiser that drew several hundreds, including musicians Kid Rock and John Rich and the former NASCAR driver Darrell Waltrip, according to a person who attended but asked to remain anonymous to discuss the private gathering at the the Four Seasons hotel.

This past week, Trump hosted the families of members of the military who died during the chaotic withdrawal from Afghanistan. The week before, he held a fundraiser for the Patriot Freedom Project, a group that supports those who attacked the U.S. Capitol on Jan. 6, 2021.

Aides say he has also focused on relationship building, calling party officials and recording videos for state and county party events. Such efforts, they say, have helped him earn him earn endorsements from senators, members of Congress and statewide officials.

They have also acknowledged the large-scale rallies that were the signature of his past campaigns — and which he was doing weekly at this point in 2015 — are expensive, especially as the former president's political operation has been diverting tens of millions of dollars to spend on legal fees defending him and his allies. In places of the rallies, Trump has given speeches at events organized — and paid for — by state parties, and made unadvertised stops at local restaurants, where he interacts with supporters.

In early-voting New Hampshire, Mike Dennehy, a veteran Republican strategist, said he thinks Trump “is doing the bare minimum necessary for him to maintain his lead." At the same time, Trump’s broader campaign “is working very hard, harder than they have have worked in the history of Donald Trump campaigns," Dennehy said.

“The contenders in the Republican primary are not giving Donald Trump much of a contest. So he has the luxury of just doing enough to maintain his lead,” he said.

Biden has campaigned even less.

The president championed a Democratic National Committee effort to make South Carolina the party's leadoff state in its 2024 presidential primary, breaking with Republicans who are still starting in Iowa. But Biden has not visited South Carolina as a 2024 candidate.

Biden's reelection campaign says his approach mirrors that of past incumbents, including Presidents Barack Obama and George W. Bush. Biden is frequently promoting his policy achievements but keeping campaign costs low, while working with national and state Democrats to bolster staff and data operations so that they will be in place when the race heats up next year.

The president has attended fundraisers around the country for his reelection campaign and visited battleground states such as Arizona on official business. Sometimes, he has gone to Republican bastions, including Utah, Texas and Alabama.

Once there, he often blurs the line between politics and the presidency, celebrating things such as the bipartisan infrastructure law approved by Congress last year, while chiding Republicans for opposing a green energy and health care package that he argues is creating jobs and lower costs for Americans.

“You get great credit for doing your job and people tend to listen to you more when you’re not talking about your own reelection but you’re just talking about enacting something that’s good for the country,” said Ed Rendell, a former Democratic governor of Pennsylvania. “That’s a real advantage. The incumbent can just go on being the incumbent."

Biden's Labor Day travels are taking him back to Philadelphia, site of his lone campaign rally. It was at the city's convention center, where some of the country's largest unions paid for a June event after announcing that they had banded together for the first time to offer a joint endorsement of Biden.

A return to Pennsylvania recalls the pandemic-marred 2020 campaign, when Biden visited the state more than any other. Even though he was a senator from Delaware, Biden was born in Scranton, Pennsylvania, and still frequently talks about his Keystone State roots.

“I think it’s indicative of a campaign that is not forgetting the lessons that were learned in 2020, when Pennsylvania got so much attention – even in the limited campaigning,” said Mike Mikus, a longtime Democratic consultant based in Pittsburgh. “If you take it for granted you could lose it.”

Of course, focusing too much on one state can create gaps elsewhere. The most glaring example was Hillary Clinton not campaigning in Wisconsin after the 2016 Democratic primary and narrowly losing the state to Trump. But Ben Wikler, chair of the Wisconsin Democratic Party, noted that Biden's first trip as president was to Wisconsin.

“This election cycle feels like the exact opposite of 2016,” Wikler said. Referring to the traditional Democratic “blue wall” of Wisconsin, Michigan and Pennsylvania, he added, "This is an administration that understands to its core that bolstering the blue wall is the path to reelection in 2024.”

___ Colvin reported from New York. Associated Press writer Jonathan Mattise in Nashville, Tennessee, contributed to this report.