For example, Hillary Clinton compared the 2000 Florida election recount to rigged elections in Nigeria. [1]
The Democrats continue to believe 2000 was rigged.
How about something more recent? Oh yeah, Hillary Clinton claims the 2016 election was "not on the level". Going much further, she calls the result "illegitimate", citing hacking (never proven) and voter suppression (no evidence). [2] [3] As recently as 4 years ago the Democrats were doing the exact same thing the Republicans are doing now.
[1] https://abcnews.go.com/Blotter/story?id=8314204&page=1
[2] https://news.yahoo.com/hillary-clinton-maintains-2016-electi...
[3] https://www.washingtonpost.com/politics/hillary-clinton-trum...