At the time Germany signed the armistice ending World War I, no battles had been fought on its territory and no foreign army had invaded it. The German people suffered greatly — food shortages and the like — but defeat to many did not seem to come from the battlefield in front but from traitorous civilians from behind. This came to be known as the “stab in the back” myth. The Kaiser believed it, Hitler used it, and now Donald Trump — not even waiting for defeat — has revived it. If he loses in November, it will be because the election was stolen from him.

“The only way we can lose in my opinion … is if cheating goes on,” he said. He was speaking in Pennsylvania and referring to Pennsylvania, where he trails Hillary Clinton by an average of nine points in the polls. But those and, indeed, any polls showing Trump falling behind are now themselves being questioned — although when he was ahead, he adored them. Once again, the diabolical hand of the mainstream media and the Republican establishment are supposedly at work. The polls are skewed. Trump is actually ahead. Something about UFOs is bound to come up next.

As a presidential candidate, Donald Trump is an aberration with a background (TV show), personal characteristics (immense self-regard) and talents (a demagogic speaking style) that are unique to him. Yet, his pernicious claim that he can only lose the election if it is stolen from him builds on a general Republican obsession about election fraud. For years now, the GOP has used the specter of cheating at the polls to try to suppress the black vote. The courts, more conservative than the GOP when it comes to conserving constitutional rights, have usually intervened, but the insistent whispering campaign has done vast damage.

We are living now with the consequences of squalid decisions made years ago by opportunistic politicians — most notably Richard Nixon, whose Southern strategy welcomed racist pathogens into the Republican Party. They have taken hold. What was once the party of Lincoln has lost not only its bearings, but its very soul. Now it has a candidate who has denied the legitimacy of the nation’s first black president by promoting the racist birther movement and openly campaigns as a bigot — anti-Muslim and anti-immigrant. He has no policies, merely resentments.

It is serious business to question the legitimacy of elections. What happens at the polls is at the very heart of our political system. It is not, I grant you, a perfect system, but we know how to do elections and, when they are over, we abide by the results. Many Americans believed that Al Gore beat George W. Bush, but they — not to mention Gore himself — accepted the outcome.

Trump, like a kid playing with matches, can start a conflagration. The GOP has already done considerable damage to the faith Americans once had in their government. It is time for the party to say, enough! Republicans who have been on the fence about Trump — party leaders like the occasionally principled Reince Priebus — have got to call a halt to this nonsense. Their enduring concern is too narrow. They should worry more about their country and less about their party.

In Germany, the stab in the back myth helped destabilize the postwar government. It became a right-wing trope, prominently advocated by the exiled emperor, who identified the culprit as “the tribe of Juda” and who advocated that “these parasites [be] destroyed and exterminated from German soil!” Hitler, never slow on the uptake, did just that. In due course, he took over a government that never quite recovered from charges that it had sold out to Germany’s enemies.

Trump has identified no one and probably would rather run a media empire than the federal government. But his amorphous charges of cheating, of fraud, of rigged elections threaten to delegitimize not just a Clinton presidency but a system that not only works, but works well. It is not Hillary Clinton or her supporters who are the culprit here, it is cowed Republicans instead. Their silence is the dagger.

Richard Cohen is a columnist with The Washington Post. His email address is: cohenr@washpost.com.