Third-party candidates rarely tip the balance of an election.

Rarely, but not never. In 1968 George Wallace actually won a state and some electoral votes, and might have cost Humphrey the election, given how close the vote totals between Humphrey and Nixon were. In 1980 John Anderson didn’t swing the election, but he was a significant factor in helping people crystalize their distaste for Jimmy Carter. In 1992 Ross Perot probably sealed George Bush’s fate, putting Bill Clinton into the White House. Ralph Nader famously tubed Al Gore in 2000.

Could the 2024 election outcome be determined by RFK Jr.? The short answer is “Who knows?,” but the longer answer is “Maybe.”

In the New York Times/Siena poll of the battleground states, released over the weekend, Trump trounces Biden in a head-to-head matchup, winning 5 of the 6 battleground states.

Throw in RFK Jr. and suddenly 24% of the voters choose to vote for him, upending the race. Chances are good that, if the election were held today, Trump would still win, but things get much dicier for both Trump and Biden. And the polling shows that RFK Jr. takes more support from Trump than Biden.

RFK’s support comes from one group mainly: the large number of people who hate both Trump and Biden, a group called “double haters.”

Voters who dislike both major-party candidates — a group known to pollsters and political campaigns as “double haters” — have been instrumental in the outcomes of the last two presidential elections, and there are now more than twice as many of them as there were four years ago. Mr. Trump carried them when he defeated Hillary Clinton in 2016, and Mr. Biden won them when he ousted Mr. Trump four years later.

Now Mr. Trump has more support from these voters in five of the six battleground states polled. Only in Arizona did more double haters say they would vote for Mr. Biden.

Overall, 42 percent of those polled who did not like both candidates said they planned to vote for Mr. Trump, compared with 34 percent for Mr. Biden and 24 percent who remained undecided.

Trump gets more support from the “double haters” for the obvious reason: people hate Trump because he is a jerk; people hate Biden because he has made their lives worse in tangible ways. Between the two the choice is pretty easy.

A large chunk of Americans would breathe a sigh of relief if one or both of these candidates were out of the race. Both the Trump and the Biden years have been exhausting for a lot of people. Trump’s years sucked for them because they could not get away from the man, mostly because of the press’ obsession with “getting” him.

Biden’s years suck for the obvious reason: Biden is a terrible president. Trump might be a jerk, but things were actually pretty good and nobody worried about a new World War. He has that going for him.

Both Mr. Biden and Mr. Trump fared worse than a generic candidate from each man’s party, the polls found. While 44 percent of battleground-state voters said they would vote for Mr. Biden, 48 percent said they would back a generic Democrat. For Mr. Trump, the number increased from 48 percent to 52 percent for a generic Republican.

Third-party candidates face an almost insurmountable barrier not just to victory, but to mattering much. It’s difficult to get on the ballot in many states, and if they aren’t on the ballot they aren’t a factor. Few people will take the trouble to write in a candidate they know has no chance of victory.

For this reason alone Kennedy faces an uphill battle, but he may have the fundraising capacity to get the job done. Certainly, the barriers facing other candidates won’t be a problem; with the name “Robert F. Kennedy Jr.” he starts off with a huge name ID advantage.

Kennedy hasn’t a shot in hell of winning, but he does have the capacity to shake up the race quite a bit.

Support for third-party candidates tends to drop the closer you get to election day, as people get leery of “throwing away” their vote. If that holds true in 2024, expect Trump to benefit. Democrats looking for a safe alternative to Biden won’t cross over to vote for the Devil Trump but might find Kennedy acceptable. People who are inclined to vote for Trump were RFK Jr. not in the race are more likely to go back home.

I think.