I think that effect may be mostly independents who have no problem splitting the ticket, with local congressmen who they feel good about, and Trump who they needed to gat rid of. They have no party loyalty, so they vote for candidates they like and against candidates they don't. And Trump did everything possible to piss off everyone not actively kissing his butt.

Is it that hard to appeal to a majority of the folks back home, when you are a congressman or senator? Just avoid getting in the national news, and make several personal appearances in your home district or state, saying all the feel good things they want to hear. Mostly just tell them they are smart and pretty. Try not to say anything that kills anybody's sacred cow, and deliver the bacon when you can.