Starting with Georgia Rep. Newt Gingrich’s ascendancy in the late 1980s, however, the Republican Party abandoned the factional model. Increasingly, it became the narrowly ideological party with little internal diversity that Goldwater had first attempted in 1964. Leadership punished moderates in Congress who deviated from the conservative line with undesirable committee assignments, loss of position within committees, lack of campaign support and official party indifference when incumbents faced challenges from outside conservative enforcers like the new Club for Growth. Pressure toward ideological conformity intensified during George W. Bush’s presidency and with the rise of the tea party. Increasingly, even the leadership found itself ideologically boxed in, pressured by the extreme fringe with allies in conservative media who demanded purity.

Republican opposition to Trump in 2020 therefore differs significantly from past patterns of intraparty dissent not only because of Trump’s character, but also because the Republican Party has become a monolith…

Since the GOP is no longer a coalitional party, Republican voters and former officials who once would have found a place in its different factions now reject the Trump brand. Former officials, without hope of regaining influence in the GOP, have denounced Trump. Moderates and principled conservatives have announced their support for Biden and the Democratic Party — a party that is still organized along factional lines and has an ideological breadth that stretches from highly progressive to fairly conservative.