Byron Tau for the WSJ:

Charges that election results might be rigged have moved from the fringes of U.S. politics to a central issue in the closing days of the 2016 campaign as Republican Donald Trump has repeatedly and without corroborating evidence suggested a fair outcome may be impossible.

The 2000, 2004 and 2008 elections were hard-fought contests that all contained scattered allegations and conspiracies of fraud or mismanagement—most notably, the largely unsubstantiated claims that the Ohio election results from the 2004 campaign were inaccurate.

But those claims have taken on an official veneer in the 2016 campaign as Mr. Trump has spent the final weeks of the race raising doubts about the integrity of his contest against Democratic presidential candidate Hillary Clinton before most votes have even been cast.

 He has accused the media, the Justice Department, the Federal Bureau of Investigation and a “global power structure” of conspiring to rig the November election against him.

At Wednesday’s debate, Mr. Trump alleged that there are “millions of people that are registered to vote that shouldn’t be registered to vote” and cast doubt on whether he would accept the election results.