One of the first things you learn when studying politics is that there are lots of people who disagree with you. Sadly, it seems increasingly common for the base of whichever party loses the presidency to latch onto some conspiracy theory to deny that they actually lost.
This blog has extensively debunked the misinformation about the 2020 election promoted by President Trump and some of his supporters. But this phenomenon didn't start there.
In 2016, democrats spread rumors that President Trump was colluding with Vladimir Putin to steal the election. This was started at the top with the phony Steele Dossier that led to the Mueller investigation. However, it took on a life of its own, with a significant number of dems believing that the Russians actually changed the vote totals, which was never even alledged.
During the Obama years, there was the birther conspiracy theory. The claim that Obama's pregnant mother took a flight to a third world country to give birth in the country of the guy who dumped her never made much sense. But some people who couldn't handle the fact that Obama was fairly popular latched onto this claim as a technicality to deny that he had actually won.
The left had its own theories to deny the legitimacy of George W. Bush's victories. In 2000, the (admittedly close) election in Florida led the left to claim he was "selected not elected". Contrary to the left's mythology, there was a full (machine) recount, Al Gore was the first to file a lawsuit, and he never asked for a statewide recount. The Supreme Court finally put a stop to the absurdity (by a 7-2, not 5-4 vote) of different counties using different standards to recount the ballots.
In 2004, some on the left focused on the Diebold voting machines used by the state of Ohio. They claimed that the machines had been rigged to deliver the election to Bush. Republicans apparently forgot to rig the 2006 and 2008 elections, which they lost badly.
I don't recall any conspiracy theories about Bill Clinton's election. Discontent with the election on the right focused on the candidacy of Ross Perot costing George HW Bush the election. While this may be true, the fact that Bush lost so many votes still signified serious discontent with his policies.
The left's rage over the 1988 election focused on the Willie Horton ad supposedly stoking racial divisions. Bush's ad never mentioned Horton's race or showed his picture. In any case, Michael Dukakis' record on crime was a perfectly legitimate issue to raise.
In 1980, some on the left promoted the "October Surpise" theory that Ronald Reagan had made a deal with Iran to prevent the release of hostages until after the election. There was never any evidence of this.
Conspiracy theories have moved beyond presidential elections. In 2018, losing dem candidate for governor of Georgia Stacy Abrams refused to concede the election. She promoted false claims that voters were suppressed from voting. She was widely embraced by the left, which largely endorsed her claims.
Dems have recently taken to promoting the idea that any effort to secure elections or limit the timeframe for voting is "voter suppression" that is akin to Jim Crow laws. They never point to even a single person who was legally eligible to vote but unable to do so.
They claim that voter ID is racist, despite massive popular support for it, including a majority of dems. Ironically, they claim that blacks are less capable of performing the basic task of obtaining an ID, a far more racist claim.
Dems are promoting HR1, the "For the People Act". Any bill with a title that saccarine is likely a scam. In addition to banning voter ID, the bill also removes all bans on ballot harvesting, a practice which actually was used to commit fraud in the 2018 North Carolina 9th congressional district election. The bill contains many other terrible provisions designed to benefit dems.
If candidates refusing to concede elections they lost becomes the norm, America will be worse off.