Mitch McConnell, discussing the 2020 US presidential election, was quoted as follows:
On Monday, Senate Majority Leader Mitch McConnell, the top Republican in Congress, said that Trump is "within his rights" to challenge the outcome, and criticized Democrats for expecting the president to concede.
“President Trump is 100% within his rights to look into allegations of irregularities and weigh his legal options,” McConnell said. “Let’s not have any lectures about how the president should immediately, cheerfully accept preliminary election results from the same characters who just spent four years refusing to accept the validity of the last election.”
What was he referring to by "spent four years refusing to accept the validity of the last election"? e.g., has he, or other officials previously made statements to that effect in more detail?
Political opponents of President Trump (i.e., Democrats) obviously were displeased by the 2016 election, and some of that might have come from the fact that Trump "lost" the popular vote even while winning the Electoral College. However, displeasure doesn't automatically rise to the level of "refusing to accept" the election results, so I assume the senator is referring to something more specific?