Mr. Trump did not invent paranoia; he did not create the Republican meme of fraudulent minority voting. He just took it — as he so often does — to an extreme. Senator John McCain made similar warnings in 2008, and murmurings of cheating go back at least to 2000, a close national election, botched in Florida, decided for George W. Bush by the conservative majority of the Supreme Court. And long before Mr. Trump entered the presidential race, Republican legislators were busy passing voter ID laws based on the fallacy of widespread fraud.Mr. Trump’s brain is a pincushion for conspiracy theories, so maybe it’s no surprise that he thinks the Clinton campaign will be sending African-Americans and foreigners into booths across the country to fake their votes over and over, millions of times.Now, more than ever, the country needs responsible political leaders and the courts to defend and expand voting rights, rather than sitting silently while Mr. Trump further demolishes public confidence in the foundations of our government.