They don't have the numbers without the Republicans joining in. Doing it before they have the numbers is just symbolism. They need to be talking to Economists about how the US is suffering economically because of his policies. That is really the only way to get Republican politicians to vote against him.
Nah, that won't work. They should absolutely be prepping for impeachment BUT the only thing that will make the Republicans turn is to actually have their state economies crater. It won't take long before layoffs, food shortages, and elevated costs for everything not only makes their re-election bids grim (what they care about most), but it also increases the likelihood they can't step into their own districts without folks walking up on them. Until they feel in multiple kinds of danger, they won't reverse course, which means we gotta go through some shyt before that happens.
I would not expect any real Republican peeloffs until late-Summer, early Fall.