Foaming at the mouth before the election, Donald Trump asserted that if he didn’t win it was because the election was “rigged.” He did not specify how the election might be “rigged”; he just asserted that it was rigged. Then Trump won Wisconsin, Pennsylvania, and Michigan by a total of 100,000 votes. These narrow victories gave him a majority in the Electoral College. If he had not won them, then Hillary Clinton would have been elected president.
“What’s sauce for the goose is sauce for the gander.” Jill Stein, the Green Party candidate for president in 2016, called for a re-count of the votes in the three states. If all three states could be “flipped,” then Trump would lose the vote in the Electoral College just as he had lost it (by better than 2 million votes) in the popular vote. She argued that Russian hackers might have messed-with the voting machines and that there had been voting irregularities. She did not identify any specific irregularities; she just asserted that there had been voting irregularities. Stein, who had raised $3.5 million for her presidential race, suddenly received $6.6 million in donations. Then the Clinton campaign, after having conceded the election, joined the Stein campaign.
“What is sauce for the goose is sauce for the gander.” Once Hillary Clinton joined the effort to overturn the results of the election, Trump responded. Trump tweeted that “serious voter fraud” had taken place in California, New Hampshire, and Virginia. “Millions of people who voted illegally” had pushed Clinton to a nominal victory in the popular vote. Trump’s claims were widely denounced as ridiculous, but they’re not more ridiculous than the Clinton-supporter financed allegations that the Russians might have hacked voting machines or that un-specified “irregularities” had occurred.
 See: https://www.opensecrets.org/pres16/candidate?id=N00033776
 “[Trump] rages as recounts advance in three states,” The Week, 9 December 2016, p. 5.