It's a little bit of both. You have your hardcore Republicans and Democrats who will always vote for their party and a lot of independents who who are just barely paying attention and vote for "the one I'd have a beer with". There's also the situation in Gaza that has people voting 3rd party to protest Biden's handling of the situation even though it'll be much worse with Trump.

A lot of others can't be bothered to vote unless it's someone they're excited to vote for like we had with Obama.