Trump’s election-rigging claim will backfire. Here’s the evidence.

In recent days, Donald Trump has ratcheted up claims of voter fraud, claiming that the Nov. 8 election may be “rigged” against him. In Wednesday’s debate, he refused to pledge that he would accept the result if he loses, saying that he would keep the nation “in suspense.”

These sorts of claims are common among sore losers in authoritarian states, sometimes not without good reason. But casting serious doubt on the outcome is a radical departure from established practices among political leaders in democratic states during the modern era — and from previous U.S. nominees in our lifetime. Trump’s claims are particularly concerning given that there is little evidence of voter fraud in modern elections.