Mitt Romney has always been a Democrat in Republican clothing. He was only nominated in 2012 because he did the best in polling against Obama, and the GOP was so desperate to get rid of Obama (much like the Democrats this year in nominating Joe Biden to run against Trump).
Everyone knew deep down that Romney was really a liberal Democrat. Obamacare was similar to the health reform measure Romney signed into law as Governor of ultra-left wing Massachusetts, but no one in the GOP talked about that. Romney’s true colors are now on stage for everyone to see.
As far as Liz Cheney goes, sure, she has criticized the President, but she has also supported him and she voted against impeachment. She isn’t endorsing Biden. And it’s not like there weren’t Democrats who criticized Obama when they weren’t happy with him.
StanHalen accusing people of being partisan is rich considering his partisan viewpoints he spews all the time.