Bound to No Party, Trump Upends 150 Years of Two-Party Rule

Until now, the American two-party system has resisted assaults from the outside for more than a century and a half. No new party has captured the presidency since Abraham Lincoln’s Republicans in 1860.

Even formidable figures like Theodore Roosevelt failed to break up the duopoly. Unhappy with his Republican successor, William Howard Taft, Roosevelt formed his own Progressive Party, also known as the Bull Moose Party, to mount a comeback in 1912, winning 27 percent of the popular vote and 88 electoral votes, but losing to the Democrat, Woodrow Wilson.

Strom Thurmond in 1948 and George Wallace in 1968 staged independent candidacies founded on overtly racial appeals. John B. Anderson, a moderate Republican congressman, ran as an independent in 1980. The high-water mark since Roosevelt came in 1992, when Mr. Perot won 19 percent of the popular vote as an independent; he ran again in 1996 and drew less than half of that.

By running within the Republican Party, Mr. Trump last year managed what they never did, while making clear that he was not really a party man. The feeling was mutual. The Republican establishment resisted even after he had won enough primaries to secure the nomination, and he repeatedly threatened to run as an independent if he felt mistreated.