Less than a week before Election Day, third-party presidential candidates still present an unknown factor in key swing states where dozens of Electoral College votes rest on the knife's edge and their getting even 1% could make all the difference.

Democrats, traumatized after third-party contenders ate at Hillary Clinton's vote share in 2016, launched a full court press early in the election cycle to kneecap groups like No Labels and candidates like the Green Party's Jill Stein, Robert F. Kennedy, Jr., who ran as a Democrat before becoming an independent and then endorsing former President Donald Trump, and Cornel West.

The Democratic National Committee pumped millions of dollars into casting them as spoilers at best and deceptive vessels of Republican subterfuge efforts at worst. Outside groups, including centrists and progressives, formed unconventional alliances to clear the way for a head-to-head matchup between Trump and President Joe Biden, and later Vice President Kamala Harris.

Operatives involved in the effort expressed satisfaction at the effort. No Labels, once floating a centrist "unity ticket," ultimately folded. Kennedy dropped out and became more aligned with Trump, possibly hurting the former president in states where he remains on the ballot. And Stein and West are stuck at the bottom of polls.

But nobody is resting on their laurels.

"Democrats are taking nothing for granted. We've learned the lessons of 2000 and 2016, when third-party candidates helped throw the White House to Republicans, and we're not going to allow a repeat of that in 2024," said Lis Smith, a communications adviser to the DNC on third parties.

Still, "we're not going to pat ourselves on the back but, but we are satisfied that we took the third-party threats seriously," she said. "At the beginning of this cycle, people were talking nonstop about No Labels and RFK, Jr. But both of them, because of what Democrats did, ended up either not running or being complete non-factors in this race."

Democrats were haunted by the 2000 and 2016 election results, when they claim third-party candidates nabbed enough swing-state votes to rob their nominees of victory. That danger would not go unheeded this year, they determined.

The DNC set up an internal group specifically designed to message against third-party candidates. Progressive groups like MoveOn and center-left organizations like Third Way banded together to help clear the runway for Biden and later Harris to face Trump one-on-one.

A third-party "unity ticket" from No Labels was kiboshed after Democrats painted the effort as a spoiler and heavily lobbied would-be candidates against joining the crusade. Digital operations were stood up to quickly highlight controversial comments candidates like Kennedy, Stein and West. Millions of dollars were pumped into advertisements highlighting backing from Republican operatives for supportive super PACs. And Democrats filed lawsuits to try to prevent other candidates from getting a spot in swing-state ballots at all.

Democrats now told ABC News they're happy that their work made a difference.

Kennedy, in part because of Democratic efforts and in part because of his own views on things like vaccines and COVID-19, was effectively viewed as more aligned with Trump than his family's political heritage. Stein, while still on the ballot in six out of seven swing states, saw her support drop to normal levels after fear that frustrations with Biden would help it jump. And Democrats no longer view West as a serious threat.

"There was a different point in the race where No Labels, where RFK was stronger, where I think the threat was a little bit more existential. I think the threat is still troubling, but I think that Democrats have worked hard to offer voters who are persuadable by third-party candidates an alternative view on what those candidates provide and also on the risk associated with parking a protest vote with those candidates," said Joel Payne, MoveOn's chief communications officer.

"Third parties are certainly a factor, but I don't know if they are the same factor at this point in the race that they were, say, six, nine, 12, months ago."

Still, their existence on ballots at all poses a risk to both parties, and there's little either can do about it.

Stein is on the ballot in the ballot in Arizona, Georgia, Michigan, North Carolina, Pennsylvania and Wisconsin. The Supreme Court denied Kennedy's efforts to remove himself from the ballot in Michigan and Wisconsin. Libertarian Party candidate Chase Oliver is also on most ballots.

Democrats can knock Stein as much as they want, and Kennedy can shout from the rooftops about his support for Trump, but operatives said they're virtually guaranteed to win over some marginal support. At the end of the day, operatives said, some voters are immovable -- and in races that are won or lost on the margins, taking even 1% of the vote can make a difference.

"If you're still a Jill Stein voter, and you think it will have an impact on the outcome that may help Trump, then in the end, we probably weren't going to get you anyway. So, I think 1% is probably realistic, but if Chase Oliver is getting 1%, that's a Trump problem too," said Jim Kessler, a Third Way co-founder.

Both parties could have particular concern in Michigan -- anger over Biden's handling of the war in Gaza could push some members of the state's large Arab population away from Harris and toward Stein, and with Kennedy still on the ballot, he risks Trump's ability to take advantage of that dynamic.

A CNN/SSRS poll released Wednesday showed Kennedy nabbing 3% of the vote in Michigan and Stein getting 2%. West also got 1% in the poll, though Oliver did not get enough support to register. In Wisconsin, Kennedy and Stein each got 1%, while Oliver and West didn't register. In Pennsylvania, Stein and Oliver each got 1%.

"They're going to get a few percentage points, and that could affect the outcome in a close election, which by all polls, it appears very, very likely it's going to be very close," said nonpartisan Michigan pollster Bernie Porn.

And in an election cycle that's already seen a president drop out, two assassination attempts, 34 felony convictions and more, any question mark presents yet another opportunity for uncertainty.

"You could see somebody playing a spoiler if the race is that tight in a lot of these states," GOP pollster Robert Blizzard said. "I don't believe Trump ever got over 50 in Pennsylvania, Michigan or Wisconsin before, and yet, he's won those states at least once before. And so, third parties, give voters who are concerned about Harris and fatigued about Trump a place to go. But I just don't know what role they're going to play

Yet Democrats have been the party most publicly wringing their hands about the threat Stein and others pose, loathe to relive their past traumas. And in the home stretch, operatives who spoke to ABC News sounded content that the party had done as much as they could.

"What we can do at this point is making sure that voters are doing this just out of laziness, that they know the repercussions of that choice. And then in the end, it's up to voters," Kessler said. "I'm satisfied that the effort is robust."