He didn’t join the Dems. His “leaving the GOP” is pretty obviously a precursor to running as an independent in 2020 against POTUS.
So according to his “thinking,” bug > windshield.
Interesting. It can only hurt the Dems; he's not going to siphon votes away from people would vote for President Trump.
LOL. Running for President? Tilting at windmills. Would the Libertarian Party nominate him. The real reason is that Amash would lose in a Rep primary. He wants to stay in Congress and becoming an Independent is his only shot.