Trump received 304 Electoral College votes in 2016. Of the 10 elections from his own in 2016 to Ronald Reagan’s first in 1980, Trump only won more Electoral College votes than George W. Bush in 2000 and 2004.
USA Today – Trump falsely claims biggest electoral win since Reagan
Wikipedia – List of United States presidential elections by Electoral College margin
Trump repeatedly claimed that the 2016 election was rigged, and cast doubt on whether he would accept the results as legitimate. He reiterated this during a debate with Hillary Clinton when asked if he maintained his view on the election.
I will look at it at the time. I’m not looking at anything now; I will look at it at the time. What I’ve seen – what I’ve seen is so bad. First of all, the media is so dishonest and so corrupt, and the pile-on is so amazing. The New York Times actually wrote an article about it, but they don’t even care. It’s so dishonest, and they’ve poisoned the minds of the voters. But unfortunately for them, I think the voters are seeing through it.
…
What I’m saying now is that I will tell you at the time. I will keep you in suspense, OK?
Trump later blamed his loss of the popular vote on mass fraud.
Politico – Trump still won’t commit to accepting election results
Politifact – Donald Trump’s Pants on Fire claim of ‘large scale voter fraud’
