The most interesting, and important, dynamic in American politics today is the existential struggle going on in the Republican Party between the establishment and the insurgents—or to be more accurate, between the hard-line bedrock conservatives (there are only trace elements of the old-line center-right bloc, much less moderates) and the radicals.
Of course, tugs-of-war between establishment forces and ideological wings are nothing new with our political parties. They have been a continuing factor for many decades. The Republican Party had deep-seated struggles between its Progressive wing, led by Teddy Roosevelt and Robert La Follette, and its conservative establishment, led by William Howard Taft and House Speaker "Uncle Joe" Cannon, going back to the turn of the 20th century.
The Progressives succeeded in stripping Speaker Cannon of his dictatorial powers in 1910, and TR's willingness to bolt the GOP and run in 1912 as a Progressive on the Bull Moose Party line killed Taft's chances of winning and elected Democrat Woodrow Wilson. The struggles continued with moderates Wendell Wilkie and Tom Dewey battling Taft's progeny Robert through the 1940s. And, of course, the insurgents' struggles continued through Barry Goldwater and Ronald Reagan. Reagan first moved into national politics in 1968, with an abortive challenge to centrist Richard Nixon, who won and governed in the middle on domestic policy, promoting liberal social policies on welfare and health reform. Reagan reemerged in 1976, and his foray against centrist President Ford cost Ford the election—but Reagan's own election as president in 1980 led to an era of relatively pragmatic center-right policy-making. At the same time, however, the ongoing regional changes in the country were eliminating the bases of moderate and liberal Republicans and moving the GOP center of gravity to a lily-white and hard-line base in the South and rural West.