Republicans have forced out anyone who doesn’t walk in lockstep with the party. They have gone as far as to run alternative Republicans in some races, causing the conservative vote to be split and forcing the incumbent Republican to lose to the Democrat. Meanwhile, Democrats will let a far-right nutter like Joe Manchin run as a Democrat because he is slightly to the left of some other even crazier bastard. Even when the Dems win a majority the Republicans do everything they can to keep elected people from being sat for as long as possible. During Obama’s term, Franken was elected, but the Republicans drug out every legal battle they could to contest his win and keep him from being seated. In the end, the Dems had an actual majority for only 4 months, and even then had to get 3 Republican votes to break the Republican filibusters.