Can you point out a time when the Dem and Reps got along famously? It's the same thing over and over.
There have always been significant philosophical differences, sometimes rather pronounced. These days the rancor isn't only over the issues; it's become personal.
Long time members of the Senate from both parties have often remarked how much worse it is now than it was, say, 30-40 years ago. It used to be that you could debate each other all day -- sometimes heatedly -- and at the end of the day, go out for a couple drinks together, drop the shop talk and enjoy each other's company.
These days disagreement on the issues is much more likely to boil over into personal hatred. When it becomes personal, you will do whatever it takes to prevent your "enemies" from claiming any credit or getting a "win." Personal vendettas are preserved over pursuit of the national interest, IMO. Anything that's even remotely a concession to the people you hate becomes a non-starter. (Hence the increasing trend of both sides insisting some things are "off the table" as a precondition to negotiations.)
The 24/7 media have a vested interest, IMO, in turning political debate into Jerry Springer. It's good for ratings. And the politicians are giving us what they think we want, apparently -- we want "our team" to not only win legislatively, but to personally ruin the "other guys."
Having said that, even these days both parties usually wind up figuring out a way to work together when it **really** hits the fan. It just feels like their unwillingness to work together at other times is leading us down that road more often.