Michael Barone:

I ascribe much of the partisan tone of today’s politics to two changes urged by the political scientists I studied in college nearly half a century ago.
One was the idea that we should have one clearly liberal and one clearly conservative party. This was a popular enough argument in the 1940s and 1950s that Gallup used to test it in polls.
Political scientists and sympathetic journalists were annoyed that there were lots of Southern (and some non-Southern) conservatives in the Democratic party and that there were a fair number of pretty liberal Republicans in big states like New York and California.
Wouldn’t it make more sense, they asked, to have all the liberals in one party and all the conservatives in the other? That way, they said, voters would have a clear choice and the winning party (the liberals, most of them hoped) would be able to enact its programs into law.
There are indeed rational arguments for this. For years Southern whites clung to the Democratic label because of memories of the Civil War, while many liberal Northerners supported Republicans because they disliked big city Democratic political machines. Neither party was ideologically coherent.
Today it’s clear that the prayers of the midcentury reformers have been answered. The Republican party is a clearly and nearly unanimously conservative party, while the Democratic party is the natural home for liberals.
As a result there are more party-line votes in Congress than there were half a century ago. There are fewer friendships and alliances across party lines. Parties with supermajorities can enact their programs (e.g., Obamacare) even in the face of hostile public opinion.

Hm. It hasn’t happened in Rhode Island yet, though. He continues:

Another idea peddled by political scientists and some thoughtful liberal politicians half a century ago was that there should be more party discipline in Congress.
Rep. Richard Bolling, frustrated that Democratic House speakers didn’t force Southern conservatives to vote the liberal line, wrote two books in the 1960s advocating this. Liberal political scientists and columnists liked the idea.
So when Democrats won big majorities in the Watergate year of 1974, San Francisco Rep. Phillip Burton, in a typical backroom maneuver, engineered the election of Democratic committee chairmen and important subcommittee chairmen by secret ballot.
House Republicans adopted a similar rule, providing for election by an elected steering committee, after their big win in 1994.
There’s a certain logic to this, and I believe the results on balance have been positive. You don’t see senile chairmen frozen in office by the seniority system (a progressive reform in 1911) any more, and both parties have generally chosen competent chairmen.
But — and here’s the answered prayers department — you also get more partisan politics. Anyone wanting a chairmanship some day had better not dissent from party orthodoxy very often.
A reputation for bipartisanship doesn’t help you get ahead when members of the other party don’t get a vote.

Instead, you get called–often quite appropriately–a DINO or RINO.