The bottom is falling out of Donald Trump’s poll numbers. In just the last week, Hillary Clinton hit 50 percent (or more) in some polling, and she leads by double digits in the last four major national polls—Monmouth, CBS News, NBC Survey Monkey, and Public Policy Polling. It’s still early, but there are other signs that Trump may be fading. On Monday, 50 top GOP security officials signed a letter saying they won’t vote for Trump, and Maine Senator Susan Collins became the sixth Republican senator to say she won’t vote for Trump (or Hillary Clinton either, to be clear).

But within Trump Nation, their hero stands tall. Trump has constructed a parallel universe of faux facts—maybe better called lies—that are now dogma for his voters. He began his rise to national political fame by claiming that President Obama wasn’t born in this country and thus was ineligible to be president, and could be a Muslim to boot; now two-thirds of his supporters think the president is Muslim and more than half say he wasn’t born here.

Those aren’t the only Trump lies that have become gospel to his people. A PPP national poll completed after both parties’ conventions ended found that 74 percent of Trump voters think Clinton should go to jail, while two-thirds say she is a bigger threat to the United States than Vladimir Putin.

A more recent PPP poll that just found Trump trailing Clinton by 2 points in North Carolina—her first lead there—also examined the extent to which Trump voters believe the tales he’s concocting on the trail. It is alarming: Sixty-nine percent of Trump’s North Carolina voters say that if Clinton wins, that means the election was rigged (only 16 percent believe it would be because she got the most votes.) Forty percent think ACORN—which no longer exists—will steal the election for the Democrats.

Almost half blame President Obama and Clinton for the 2004 death of Capt. Humayan Khan in Iraq, even though Obama was an Illinois state senator at the time. Likewise, 47 percent believe they saw a video Trump claimed showed Iran collecting $400 million from the United States, even after Trump admitted the video didn’t exist. And after Trump called Clinton “the devil” last week, 41 percent agree she is, in fact, the devil. But here’s some good news, 42 percent actually disagree (17 percent just aren’t sure).

“What Trump has revealed is that there are parts of the Republican base that are not connected to the mainstream of the Republican Party, and those folks seem susceptible and receptive to conspiracy theories,” Mark Fenster, author of Conspiracy Theories: Secrecy and Power in American Culture, recently told Bloomberg’s Sahil Kapur.

The propensity of Trump voters to believe his lies is especially worrisome now that he’s aggressively pushing the idea of a “rigged election” as his poll numbers worsen. “I’m afraid the election’s gonna be rigged, I have to be honest,” he claimed last week in Columbus, Ohio. In Virginia, he blamed the “dishonest machine” around the Clintons for the coming theft. He told Fox News: “I’m telling you, November 8th, we’d better be careful, because that election is going to be rigged. And I hope the Republicans are watching closely or it’s going to be taken away from us.”

And indeed, some GOP pundits are “watching”—and pushing Trump’s evidence-free claims. Fox News’s Sean Hannity has revived the old myth of voter fraud in Philadelphia in 2012—earning a rebuke from CNN’s Brian Stelter. Unfortunately, CNN is also helping to propagate Trump’s voter-fraud myth with its infamous dog-whistling commentator Jeffrey Lord, who has been pushing either very old or very false (or both) fraud claims this week. Voting-law expert Rick Hasen has taken Lord down on Twitter. If only CNN would have him on to refute Lord’s lies in real time.

The bottom line is that even if Clinton wins, the conspiracy theories peddled by Trump will likely undermine her mandate. “The worst possible scenario here would be one in which no matter how the election turns out—suppose Clinton wins in a walk, or the race tightens—Trump refuses to accept it,” Fenster told Sahil Kapur. “Or maybe Trump accepts the results but his supporters, particularly the more extreme ones, refuse to accept it. That seems deeply problematic.”

It was heartening to see so many Republicans reject Trump’s attacks on Khizr and Ghazala Khan after their poignant remarks at the Democratic convention. It’s now time for Republicans to challenge Trump’s wildest claims, especially about voter fraud and election “rigging,” or else face down an angry GOP base that refuses to accept a legitimate American election. One could argue that GOP obstruction of both Bill Clinton and Barack Obama represented the rejection of a legitimate election, and some Republican leaders may see the angry Trump supporters as an aid in thwarting Hillary Clinton, too. But encouraging millions of people to believe lies about our democratic election process is undermining democracy itself. Some Republicans, at least, have to believe that, and speak out against these toxic lies and Trump’s manipulation.

And in the end, some anti-Trump Republicans are probably going to have to do more than say they don’t support the GOP nominee. By October, it may be that the only honorable stance is to tell other Republicans that they themselves will vote for Clinton—and to ask that these GOP voters do too. A Clinton landslide would help dispel claims of voter fraud and election rigging—and also prove that Trumpism is an angry dead end. That should appeal to anyone who hopes to be part of a vibrant national party.