1972, Democrats lost and they sought to overturn the election by impeaching the Republican president.
1980, Democrats lost and they sought to overturn the elections (also 1984) with investigations into the Iranian hostage release and Iran-Contra.
1988, Democrats lost and they sought to overturn the election with “Brought to Light” investigations into Bush’s CIA activities.
2000, Democrats lost and the sought to overturn the election first with crackpot “Bush knew” conspiracy theories (even Hillary made the claim from the floor of the Senate) and then with talk of “war crimes” and “torture”.
PUSH BACK AT THE RATS
It was not the GOP who created this era of hostility in American politics.
Exactly right. Newt Gingrich wasn't in Congress yet in 1974 (I think he got elected in 1976 iirc -- I should know, since he ran in my old Ga. congressional 3rd district before I moved away in 1975), but he placed the blame with the Democratic "Watergate Class" of 1974 and 1976, who came into office with hidebound liberal moral and intellectual smugness and promptly began to break down the old collegiality by e.g. reducing the number of GOP seats on congressional committees and changing procedures to limit Republican comments and amendments.
Gingrich knew what he was talking about, and his willingness to buck marshmallowy RiNO's like House Minority Leader Bob Michel of Illinois who just took all the guff and abuse is what got him the Speaker's chair, that and the Contract with America.