Picking up on arguing against the idea that both sides are getting too/more extreme....
1. Trump brought in a bunch of first time republican voters. I think we would all agree they are not moderate Republicans, the new voters came in as part of pushing out the RINOs. Forgive me being lazy and not putting in links, but I do recall articles about trump driving turnout in 2016 and it being lots of new voters (not young, just people who hadn't voted before).
2. Moderate Republicans left the party. Some stayed home, others crossed the aisle and went with the democrats. Mix this with the above (and population growth), and record high turnouts for both parties make sense.
3. That's changed the makeup of the Ds and Rs ever since.
4. Political parties represent their members. If they don't, the members leave. They tend to go towards the middle of whatever their group is, if they go too far in catering to any particular group of constituents they risk losing support of the others. The abortion situation is a good example.
5. Democrats picked up a bunch of moderate republicans...so as a whole group that moved them to the right. To keep those voters the democrat party moved that way as well. Republicans lurched further right, they both lost their moderates and picked up people further right.
6. As such, the argument that the dems went left doesn't make sense.
Yay/nay???