Here's Hilary.
The Dems and MSM were arguning that the election was stolen for 4 years when Trump won in 2016.
So no, it is really not "a strictly Republican/MAGA thing".
Link: https://www.nationalreview.com/the-morning-jolt/hillary-clintons-bad-habit-of-questioning-election-results-has-spread-to-all-democrats/