We don’t need to have major-party presidential nominees to have a conversation about a third-party spoiler candidate affecting the 2024 presidential election. Faced with the prospect of a rematch between President Biden and former President Donald Trump, at least two alternatives have already emerged: The bipartisan No Labels organization is working toward fielding a centrist presidential ticket, while Cornel West, a well-known public intellectual and political progressive, has launched a bid for the Green Party’s nomination.

These efforts have Democrats fretting that both bids could garner support from voters who might otherwise back Biden against Trump, thereby boosting Trump’s chances of winning. So what do we know about the situations in which third-party bids become spoiler campaigns?

Initial evidence suggests that, in a rematch between Biden and Trump, a No Labels and/or West campaign could pull marginal support from Biden and subtly shift the election toward Trump. Whether this would actually make for a potential spoiler, though, is a different question: History — and common sense — suggest that these possible third-party candidates would be most likely to affect the outcome if the overall race were close. But in our deeply divided political era, close elections have been the norm, which makes a spoiler candidacy a live possibility.

Since late May, five surveys have tested potential nominees for the No Labels ticket or West’s Green Party candidacy.¹ In each poll’s head-to-head matchup, Biden either held a small lead over Trump or the two were tied. But when pollsters added in West or a hypothetical No Labels candidate — Democratic Sen. Joe Manchin of West Virginia or former Republican Gov. Larry Hogan of Maryland — Trump gained a little ground and usually took the lead.

These surveys offer different explanations for the small shift in margin toward Trump when a third-party option is included. Across the polls, Trump tended to more firmly hold on to Republicans than Biden did Democrats, while the shifts in preferences among independents were inconsistent. Data for Progress’s poll examining Hogan’s possible impact found that Trump benefited from Biden’s reduced advantage among independents, while Echelon Insights’s survey testing Manchin found more Democrats broke away from Biden to select Manchin than Republicans left Trump. Meanwhile, polls from Emerson College and Echelon Insights measuring West’s impact found the progressive mainly cutting into Biden’s support among Democrats, although the Emerson survey also showed more independents shifting away from Biden than Trump.

Now, we should be cautious about reading too much into these surveys. After all, we are talking about small overall movements that lie inside the margin of error for each poll. That consideration also applies when trying to analyze who shifted, given that margins of error are larger for subgroups within a survey’s overall sample. More broadly, surveys conducted this far out from the general election historically have had little predictive value. Additionally, third-party candidates often poll better farther away from Election Day, when the stakes of the election are lower — and millions of dollars in general election advertising have yet to be spent. And finally, not every third-party voter would vote for a Democrat or Republican if their preferred candidate didn’t run, so we can’t assume that, say, a Green Party voter would back a Democrat or a Libertarian would vote Republican.

Nevertheless, these early polls demonstrate how a third-party option could affect the election and potentially boost Trump in a rematch against Biden. Let’s look at a hypothetical scenario using the 2020 election. Biden won the national popular vote by about 4.5 percentage points, but he carried Wisconsin — the “tipping-point state” that gave him a majority in the Electoral College — by just under 1 point. We can’t know precisely how a national swing to the right of the magnitude found in these early surveys might’ve played out in each individual state, but suffice it to say that a shift of 1 to 2 points in margin toward the GOP could have handed Trump victory via the electoral votes in Arizona, Georgia, Pennsylvania and Wisconsin — all of which were decided by margins under 1.2 points. Given that recent presidential elections have been close — we live in an era of intense partisanship in a pretty evenly divided country where five of the past six had a national popular vote margin smaller than 5 points — there’s ample evidence to suggest that 2024 will be another close election, by historical standards. 

To be clear, third-party campaigns don’t have to care one iota about how their presence might affect an election. They want to offer something they believe the major parties aren’t giving voters, in this case an unambiguously progressive platform (West) or a bipartisan and centrist-minded approach (No Labels). However, No Labels in particular has found itself mired in conversations about how it might potentially help Trump. Some former friends of No Labels, such as the centrist Democratic outfit Third Way and moderate Democrats on Capitol Hill, have criticized its efforts because they might benefit Trump. No Labels’s connections to some GOP donors have also prompted accusations that the group’s presidential campaign is a vehicle aimed at — wittingly or not — helping Trump win, a claim No Labels rejects.

In an interview with FiveThirtyEight, Ryan Clancy, No Labels’s chief strategist, pushed back against the notion that a No Labels ticket would act as a spoiler. “What is a spoiler?” he asked rhetorically. “One, it’s a candidate who isn’t going to win. Two, it’s a candidate whose votes would come almost entirely from one side.” Clancy argued that unlike, say, a Green Party candidate pulling mostly from the left, a No Labels ticket would seek to attract similar shares of support from independents who lean toward either party by offering a truly viable third option — a rarity in most presidential elections. Clancy cited Ross Perot’s campaign in 1992 as precedent for how No Labels hopes to broadly appeal to the electorate. Back then, exit polls suggested Perot’s voters would’ve split evenly between incumbent Republican George H.W. Bush and Democrat Bill Clinton, and around one-fifth would’ve voted for a different third party or wouldn’t have voted at all.

West did not respond to a request for comment.

Clancy explained that the group’s initial polling in December suggested that around 3 in 5 voters would consider backing a “moderate independent” candidate for president. If the group could win 3 in 5 of that universe of voters, it could get to 270 electoral votes. But if that ceiling of support becomes significantly lower in the next six to nine months — before the group’s April convention — then No Labels would take that as a “warning sign” that its ticket can’t win. “There is absolutely an outcome where we may not offer our ballot line to anybody,” Clancy said.

While No Labels understandably pointed to the Perot example, a potential centrist ticket isn’t guaranteed to take roughly the same from each major party. In the 1980 election between Democratic incumbent Jimmy Carter and Republican Ronald Reagan, moderate independent John Anderson won roughly 7 percent nationally and may have cost Carter victory in some Northeastern states, as the ABC News exit poll suggested Anderson’s supporters would’ve split for Carter 49 percent to 38 percent over Reagan. To be sure, Anderson didn’t “spoil” the election for Carter (Reagan won easily), but he did take more from one side and likely affected the outcome in a few states.

And two other third-party contenders from the past 60 years also attracted a disproportionate share of voters who might have otherwise supported one major party in close elections. In the extremely tight 2000 election, one study estimated that 60 percent of Green Party nominee Ralph Nader’s nearly 100,000 voters in Florida might’ve preferred Democrat Al Gore to Republican George W. Bush, which would’ve probably flipped the decisive state — and the election overall — from Bush to Gore. And in 1968, Republican Richard Nixon won while only edging Democrat Hubert Humphrey by less than 1 point in the popular vote, even as independent segregationist George Wallace won roughly 14 percent nationally and carried five Southern states. Yet Nixon might’ve had a more comfortable victory had Wallace not run: Gallup’s pre-election polling found voters who backed Wallace strongly preferred Nixon to Humphrey.

Early 2024 polls demonstrate how, in a close election, third-party campaigns from the center and left could potentially help Trump against Biden. Of course, other scenarios could also drastically alter the electoral environment. For instance, if Florida Gov. Ron DeSantis were to win the GOP nomination, a May poll from Ipsos/Reuters found that Biden would be primed to easily defeat DeSantis if Trump — who has not agreed to sign a pledge to back the eventual GOP nominee — ran as a third-party candidate and split the Republican vote. We are still months away from having a firmer idea about how third parties might shake up the 2024 race — but they definitely could.