There may be no more presidential debates in 2024, but will it make much difference?

The 2024 presidential race is barely underway and the last debate may have already happened.

Republican front-runner Donald Trump declined to attend any of the five primary debates so far, indicating that he saw no point because of his large polling lead.

And after the Iowa caucuses, former South Carolina Gov. Nikki Haley vowed that she would not participate in another debate unless her opponents included Trump or President Biden, effectively ending all future such events.

Haley placed a distant third in Iowa and soon lost by double digits to Trump in the New Hampshire primary -- but she has emerged as the main Trump challenger in the GOP after Florida Gov. Ron DeSantis ended his campaign.

So far, though, like Trump's other rivals, she has failed to lure him on stage.

On Saturday at a rally in South Carolina, Haley invited Trump to participate in a primary faceoff -- calling it the "ultimate mental competency test" for presidential candidates.

"Let's see what happens. Let's let this election play out the way it's supposed to play out," she told the audience in South Carolina.

That's unlikely to sway Trump: His campaign, and an increasing number of Republicans, have signaled that they expect he will cruise through the remainder of the primary and should be focusing on a likely general election rematch with Biden.

If that's what happens, there may also be no debates during the general, which would be unprecedented in modern American presidential politics, experts said.

In April 2022, the Republican National Committee voted unanimously to withdraw from the Commission on Presidential Debates -- a nonprofit and nonpartisan organization that has sponsored and produced all presidential and vice-presidential debates since 1988.

RNC Chair Ronna McDaniel called the group "biased" and accused them of refusing to "enact simple and commonsense reforms" in an official statement following the party's withdrawal. (The commission did not respond to a request for comment for this story.)

Without the GOP's cooperation with the CPD, it's unclear how the general election debates would be scheduled.

Trump, for his part, said in December that he'd still do debates through the commission. "They're terrible. With that being said, I would do 20 debates, even if it was organized by them. I would do as many debates as they want," he told Hugh Hewitt then.

The Biden campaign was more circumspect. The deputy campaign manager, Quentin Fulks, declined in December to commit to future debates.

"The campaign is going to take a look at the schedule, and we can have those conversations. But as of right now, our focus remains on building a campaign and infrastructure," Fulks said.

Do debates make a difference?

The first televised debate between presidential candidates was between John F. Kennedy and Richard Nixon in 1960, and general election debates became customary after the 1976 presidential election -- occurring every four years since Jimmy Carter and Gerald Ford battled three times on national TV.

While the lack of debates in 2024 would be historic, Dean Lacy, a professor of government and director of Dartmouth College's program in politics and law, said he isn't sold on just how much general election debates do to influence voters' political opinions.

Lacy said that primary debates seem to have more impact on shaping voters' views of candidates. Because there is typically a wider field of candidates who often have overlapping policies, as members of the same political party, primary debates can offer some distinction between generally like-minded candidates.

General election debates are different, Lacy feels.

Though they are widely watched -- the first of two debates in 2020 between Biden and Trump was seen by at least 73 million people -- "I think it's hard to say whether debates make much difference," Lacy told ABC News.

"And people who are watching them have probably made up their minds already, even if they tell us that they haven't," Lacy said.

That assessment is likely to be even more true in the case of a rematch between Biden and Trump.

In that case, Lacy said, "I think most of the effect will be not on switching the voter from Trump to Biden or Biden to Trump but from switching the voter from Biden or Trump to staying at home on Election Day."

Still, Lacy warns that a general election absent of the customary presidential debates could depress voter turnout in other ways.

"It may keep those swing voters from caring enough to go to the polls if the candidates don't care enough to debate," he said.

Some presidential debates in recent election cycles have also been markedly different, in style and tone, from those in decades past: Lacy said they "no longer look presidential."

For example, former President Trump hurled personal insults on stage in 2016 and 2020 and was quick to attack moderators on social media after debates -- making them "less respectful," in Lacy's view.

He said the debates often also lack policy discussions that are detailed enough to capture the different positions for the public.

"The debates tend to focus on issues but not in enough depth for the candidates' positions to become fully known to voters," he said.

Lacy links this to a larger phenomenon.

"I think that the candidates' decline in debating abilities, ability to tell the truth, in their political experience, is a cause of decline in public [trust] of political institutions," he said. "We see that in all kinds of metrics of decline of public trust."

What voters think

Thalia Floras, a lifelong Democrat-turned-undeclared voter from New Hampshire, said she wasn't "surprised" that Biden and Trump may not debate.

"Both of those men have more to lose by debating than if they stay home and keep their mouth shut," she told ABC News.

Floras said she isn't sure if Biden would come off as "sharp-witted" on stage, and she speculated that it would probably be for the best for Democrats if he didn't debate Trump.

However, she said, the prospect of no general election debates was not good for the country.

"It's unfortunate for the American people," she said. "This is not what is tradition and it's not what we expect."

Marykate Tillinghast, a junior at Saint Anselm College in Manchester, New Hampshire, shared this sentiment. She said that debates are "essential to democracy" and despite her lack of confidence in the quality of a Biden-Trump debate, she said it should happen.

"I think that while a debate might end up being like a quarrel among siblings, it is essential for independent voters when casting their vote," she said.

Lauren Blois, a sophomore at Saint Anselm College, hopes the presidential candidates do duke it out in a debate. She said voters need to be informed before heading to the polls, and debates are important for that.

"As a young, first-time voter, I want to hear what candidates think about certain issues that Americans are facing every day," she said. "I hope that the nominees of each party participate in a debate so every voter can cast an informed vote."

There's one other wrinkle: A prominent third-party candidate, especially given some voters' professed unease about a Biden-Trump rematch, could create pressure for a general election debate, Lacy said -- something that hasn't happened since Ross Perot was on stage with Bill Clinton and George H.W. Bush in 1992.

Lacy insisted that he doesn't think a lack of debates this year spells the end of debates in future cycles. In four years, 2028 will likely bring new faces into the presidential race -- and those candidates will need to get on a stage and on TV to generate name-recognition.

But he did express concern about what it signifies for the overall health of American democracy.

"I think it is alarming when the major party candidates not only cannot agree on the issues of the conversation but they can't agree on how to have the conversation," he said. "I don't know what the next step is for democracy."

In what Lacy said has already been "a weird election year," no general election debates would make it even weirder.

ABC News' Gabriella Abdul-Hakim, Hajah Bah, Libby Cathey, Fritz Farrow and MaryAlice Parks contributed to this report.