Errrr, the Oreinstein thesis about moving to the center is nonsense. There is NO center in American politics. There are only two large coalitions that capture all segments of American society including class, income, physical location, geography, occupations, lifestyles, etc.
With single member districts it's simply impossible to create any sort of different political structure ~ it will always take 50% + 1 vote to win an election.
The losers are forced to form a coalition as well.
Consequently America's political spectrum is not laid out on a BELL SHAPED CURVE ~ rather it's best described as a bi-modal saddle!
Back to the "center", it doesn't exist. However entire factions or large chunks of factions occasionally jump from one poll to another.
E.g. blacks moved to the Democrats in two large well known events we can call ROOSEVELT and JOHNSON
Southern whites moved to the Republicans in about 4 smaller steps ~ twice with Nixon and twice with Reagan, and possibly earlier with Eisenhower, again twice. The latest movement was with George Bush.
Obama's election saw some backsliding when Southerners once again listened to the Socialists siren song of pie in the sky and new blocks for your old car parked in the side yard.
I think Souvrn'rs are over that now.
Republicans haven't dragged anybody to the Right, there being no such creature here, but they have hurt the Democrats in recent elections ~ and the TEA Party faction within the coalition has hurt the Reacharound guys ~ formerly known as bipartisans, their time has come and gone ~ about 12 years ago. Nobody is looking for bipartisanship anymore since the Democrats have been taken over by the 15% who subscribe to cold hard Stalinist socialist theory.
The "incivility" and lack of the old palsy-walsy ways began when the "Watergate generation" elected in 1974 came to office bursting with the pus of moral smugness, and promptly began to broom Republicans aside as relics of history. In 1977, I think it was, the Democrats unilaterally reduced Republican membership on all the significant committees, and other insults and slights followed.
They had occasion to regret that contumely when Ronald Reagan's coattails gave the Senate to the GOP and the Senate majority leader's job to Howard Baker of Tennessee.
But the House remained in Democratic hands for another 14 years, and the House Democrats never learned anything along the way, except not to steal from the House Post Office.
Nice analysis.