I said caucus with the Democrats, not become Democrats. When it comes to votes that promote sedition, they might vote with Democrats when they vote against that sedition. They can still be conservative and Democrats can be a mix of liberal, centrist, and conservative. The Trump Party, on the other hand, seems to be the Party of lawlessness, anti-democracy, pro-Putin, etc. Everything the two mainline Parties have agreed to oppose over the years. So a coalition to defeat the Trump Party might be possible.
Once that garbage is buried in the landfill, they can return to arguing over their respective positions.