Another excellent piece by historian Heather Cox Richardson well worth reading, here is an excerpt. 
"With his attempt to use foreign policy to get himself reelected, Trump took attacks on democracy to a new level. In July 2019, he withheld congressionally appropriated money from Ukraine in order to force the country’s new president, Volodymyr Zelensky, to announce he was opening an investigation into the son of then–Democratic presidential hopeful Joe Biden. That is, Trump used the weight of the U.S. government and its enormous power in foreign affairs to try to hamstring his Democratic opponent. When the story broke, Democrats in the House of Representatives called this attack on our democracy for what it was and impeached him, but Republicans voted to acquit.
It was a straight line from 2019’s attack to that of the weeks after the 2020 election, when the former president did all he could to stop the certification of the vote for Democrat Joe Biden. By January 6, though, Trump’s disdain for the law had spread to his supporters, who had learned over a generation to believe that Democrats were not legitimate leaders. Urged by Trump and other loyalists, they refused to accept the results of the election and stormed the Capitol to install the leader they wanted." *
*H.C.R.