Joe Biden and Donald Trump clinched their parties' respective 2024 presidential nominations weeks ago, setting up the first White House rematch since the mid 20th century.

Still, tens of thousands of primary voters continue to cast ballots against them both, underlining an issue with rallying the base that each candidate has acknowledged.

Can President Biden overcome the dissatisfaction of people who have been choosing "uncommitted" and similar options in the Democratic primaries, largely in opposition to his policies on the Israel-Hamas war?

And, similarly, will former President Trump by November woo back Republican primary voters who have been sticking with former rival Nikki Haley, a month after she left the race?

The answer won't be clear until November.

While Tuesday's primaries showed that the amount of non-Biden and Trump votes is relatively small compared to the voters backing them, they could still be influential if the 2024 election is close and decided by a handful of narrowly divided states, as happened in 2016 and 2020.

Take Wisconsin, for example.

Tuesday's primary results showed Biden and Trump both losing more votes, among their parties, than the total number of votes that decided Wisconsin in the last two general election cycles.

On the Democratic side, with 97% of the expected vote reported so far, about 48,000 people voted for "uninstructed" over Biden.

And on the Republican side, with 99% of the expected ballots reported, about 76,000 voters chose Haley over Trump.

Wisconsin was decided in the 2016 general election by about 23,000 votes and in 2020 by even less, just 20,000 votes.

That's not the only example in a swing state.

In Arizona's nominating race in mid-March, which did not have an "uninstructed" or similar option, about 45,000 Democratic voters still chose someone else than Biden -- and about 132,000 Republican voters cast ballots for a Republican candidate other than Trump, though Arizona's voting period included two weeks in which Haley was still running before she ended her bid.

In 2020, Biden won Arizona in the general election over Trump by just 11,000 votes.

History suggests that the bases of the major parties -- no matter how fractured they become by policy and personality differences during primaries -- largely rally back around their nominees, eventually.

And past successful presidential candidates have had to deal with a notable minority of primary voters not choosing them.

In 2012, when President Barack Obama ran for reelection and didn't face any serious organized opposition among Democrats, more than 40% of the ballots in Kentucky (about 87,000) still went to the uncommitted option; in North Carolina, a "no preference" option got about 200,000 primary votes instead of going to Obama; and in Alabama, uncommitted got about 45,000 votes.

Obama went on to win the general election -- though he lost the swing state of North Carolina to GOP nominee Mitt Romney by approximately 92,000 ballots.

This year, Biden and Trump have taken steps to win over their skeptics and each others, too -- with Biden making appeals to Haley's supporters and the Trump campaign reaching out to Muslim and Arab Americans in battlegrounds like Michigan and Pennsylvania.

But 2024 is unlike the past several decades of elections in multiple ways.

The Biden-Trump rematch is the first such election repeat in the U.S. since 1952 and 1956. (In the 19th century, the same presidential candidates ran against each other multiple times.)

What's more, with Biden and Trump quickly clinching their nominations in the primary race, the country now faces the longest general election season in recent history -- more than seven months -- at the same time that polling, for now, reflects an unusual degree of uncertainty, according to 538.

As 538 also notes, another unusual dynamic this year is how disliked both Biden and Trump seem to be: Both men have negative approval ratings and, combined, they have an average disapproval rating that is higher than any presidential race since 1980.

That has drawn more attention to the so-called "double haters" who don't like either candidate. Just like with the non-Biden and Trump primary voters, their decisions in November are seen as potentially influential, if they decide to vote.

"I don't even want to vote anymore … it's a nightmare," Joann Kama, a retired African American voter from Amityville, New York, recently told ABC News.

Saying she feels "so discouraged" about the current election and politics in America, Kama said that for the moment, she doesn't plan to cast a ballot in November.

John Jackson, a voter from Florida who said he is not currently employed, likewise told ABC News in a recent interview that he plans on voting in the general election but he's "not excited" about it.

"I just don't approve of either candidate at this point," said Samantha Guerrero, a Republican from Austin, Texas. "I don't want another four years of either one of them."

ABC News' Gabriella Abdul-Hakim, Juhi Doshi, Isabella Murray and Oren Oppenheim contributed to this report.