Their parties have historically been on diametrically opposite sides of the political spectrum.
But Republican presidential nominee Donald Trump and Green Party presidential standard-bearer Jill Stein have more in common than you might think.
Here are the six things Trump and Stein have in common.
The enemy of my enemy is my friend
What draws both Trump and Stein together is that they share a common foe in achieving their goals: Democratic presidential nominee Hillary Clinton.
Trump hopes independent voters and other traditionally Democratic-leaning working class voters pick him in November.
Meanwhile, Stein is betting that liberal voters will bail on Clinton and vote "Jill, Not Hill."
To be sure, Trump has much more of a chance of beating Clinton and inhabiting 1600 Pennsylvania Ave. than Stein — who instead appears to be on a mission to merely win enough support for the Green Party to garner more influence in politics.
But both are on the attack against Clinton, who can thwart both of their political quests.
They've stoked vaccination fears
In recent years, there's been a growing number of people convinced that vaccinations cause autism — a claim that's been widely debunked by science and medicine.
Still, that hasn't stopped both Trump and Stein from stirring the anti-vaxxer pot.
In March 2014, Trump tweeted about a spurious correlation between "massive shots of many vaccines" and "AUTISM."
He repeated the vaccination concerns again in a GOP primary debate last fall.
"Autism has become an epidemic. Twenty-five years ago, 35 years ago, you look at the statistics, not even close. It has gotten totally out of control," Trump said at the debate. "I am totally in favor of vaccines. But I want smaller doses over a longer period of time. Same exact amount, but you take this little beautiful baby, and you pump — I mean, it looks just like it's meant for a horse, not for a child, and we've had so many instances, people that work for me."
Trump later clarified in a tweet that he didn't mean vaccinations as a whole caused autism, just massive doses of vaccinations — an equally out-of-the-box statement.
Stein, a Harvard-educated physician, hasn't gone as far as Trump in saying vaccines cause Autism.
But she did cast doubt about how many vaccinations were needed, citing the "corporate influence" of the "pharmaceutical industry," echoing the rhetoric of anti-vaxxers.
"I think there's no question that vaccines have been absolutely critical in ridding us of the scourge of many diseases — smallpox, polio, etc. So vaccines are an invaluable medication," Stein told the Washington Post in an interview at the Democratic National Convention last month. "Like any medication, they also should be — what shall we say? — approved by a regulatory board that people can trust. And I think right now, that is the problem. That people do not trust a Food and Drug Administration, or even the CDC for that matter, where corporate influence and the pharmaceutical industry has a lot of influence."
Stein has since clarified her statements, telling NPR, "Vaccines are a mainstay of public health. Period."
They are anti-free trade
Trump has broken with traditional Republican policies to voice his opposition to America's trade agreements.
He's said agreements like the North American Free Trade Agreement and caused massive trade deficits and shipped jobs overseas. And he's pledged that only he can negotiate better agreements to bring jobs back home.
Stein has also railed against trade agreements, saying she backs "fair trade" over trade agreements that she says benefit companies over average workers.
Both appear to be Luddites
Trump is not a fan of computers.
He's said he doesn't believe in email, and has staff print out emailed communications for him to read.
In a news conference in Florida in late July, Trump confirmed his anti-email stance.
"I'm not an email person. I'm not an email person myself. I don't believe in it 'cause I think it can be hacked, for one thing. But when I send an email, I mean... if... if I send one, I send one almost never. I'm just not a believer in email. A lot of people have told me that, including Hillary."
And during an event in Colorado, he said the military should communicate via couriers and not electronic channels.
"I like the old days, especially for the military," Trump said. "You want to attack or you want to do something, it's called courier, it's called let's put it in an envelope and let's hand it to the general. Let's not send it over the wires so everybody's probably reading it. And no matter how good they say it is, I mean people can hack it I guess, it's just terrible."
Stein has also made quizzical comments about technology.
During an education conference in March, Stein was asked whether she thought wireless Internet had a negative impact on child development — another fear that's been widely discredited by actual science.
"We should not be subjecting kids' brains especially to that," Stein said of WiFi. "And we don't follow that issue in this country, but in Europe where they do, they have good precautions around wireless — maybe not good enough, because it's very hard to study this stuff. We make guinea pigs out of whole populations and then we discover how many die. And this is like the paradigm for how public health works in this country and it's outrageous, you know."
Both have a complicated relationship with Russia
Trump's ties to Russian President Vladimir Putin have been a hot-button issue on the campaign trail.
Putin — an antagonist toward the West — praised Trump, who in turn praised Putin for praising him.
Trump also claimed to have had a relationship with Putin, thanks to appearing on the same episode of 60 Minutes.
And he hasn't denounced Putin's possible meddling in the current election, including Russia's likely hacking of Democratic National Committee emails.
All of the connections have led Clinton's campaign to question whether Trump has a dangerous relationship with Russia.
Stein, too, has a complicated connection to Russia.
Video surfaced recently of a trip Stein took to Russia this winter for a conference, where she said America needs to "reform and revise our foreign policy so that it is based on international law, human rights and diplomacy."
It was an interesting message to send from a country that Human Rights Watch — a nonprofit that tracks human rights violations around the globe — says intimidates and punishes Russians who criticize the Russian government.
They both want Bernie Sanders' voters
Trump, who is hoping to ride an anti-establishment wave into the White House, has sought to appeal to the voters angry that their candidate, Senator Bernie Sanders, is not the nominee.
Trump has repeated Sanders supporters' stance that the primary was "rigged" against Sanders, despite Sanders himself rejecting the claim.
He's also played up his anti-trade message that overlaps with Sanders' own comments throughout the campaign.
Stein, too, has been wooing "Bernie or Bust" voters who have vowed never to vote for Clinton.
She appeared at a Bernie or Bust rally in Philadelphia, as Democrats gathered to nominate Clinton at the Democratic National Convention.
However Sanders has endorsed Clinton. And he's gone as far as telling his supporters not to vote for Stein.
Polling also shows neither have been very successful at wooing Sanders voters.
The latest Bloomberg Politics poll shows 93% of Sanders supporters are voting for Clinton in November.