Democrats developed an interesting strategy in the last couple of election cycles. They ran relatively conservative candidates in districts where Republicans had held sway for a decade or more. The strategy "worked" in the sense that they elected more Democrats. These conservative Democrats are known as the Blue Dog Democrats.
Now, however, Democrats are discovering the downside of this big tent strategy. The new conservative Democrats, understanding what it will take to be reelected in districts that lean to the right, sometimes refuse to go along with the rest of the party.
Intra-party conflict infuriates the more liberal elements of the Democratic party. It also provides an opportunity for minority Republicans to have some power, by allying with the Blue Dogs.
Here we see the downside of pursuing a "big tent" philosophy: it includes in the party people with whom we do not agree. The Republicans have experienced this phenomenon with the two Senators from Maine, who call themselves Republicans but often vote with the Democrats.
Isn't politics fun?