Still, Mr. Bannon showed no signs of backing off, appearing at a fund-raiser the next night for a challenger to Mr. Flake as Breitbart News, the website he runs, featured stories on his efforts to line up donors for other primary challengers. “We’re putting together a grass-roots army,” he said in a speech in California on Friday night.
The historical parallels to F.D.R. and 1938, while inexact, are intriguing. Like Mr. Trump, Roosevelt was piqued by opposition from members of his own party and set out to replace them with more ideologically aligned candidates who would support his agenda — in his case, liberals who would take out Southern conservatives. But voters resented the intervention and repudiated him by re-electing nearly all of his Democratic rivals.
“His attempt to purge the party of conservative Democrats proved to be a serious mistake,” said Robert Dallek, whose biography “Franklin D. Roosevelt: A Political Life” will be published next month. “He lost every primary contest except one, and 60 percent of the country disapproved of his purge.”
Although born out of frustration, Roosevelt’s purge was part of a desire to force a party realignment. In those days, both parties had liberals and conservatives. Roosevelt in effect was trying to make the Democrats the more uniformly liberal party while leaving the Republicans as the conservative party. He would fail, but in decades to come, that realignment would eventually occur on its own.
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“His goal was two responsible, unified parties to replace, as he said, ‘Tweedledum and Tweedledee’ parties,” said Susan Dunn, a Williams College historian and author of “Roosevelt’s Purge,” the definitive book on the 1938 election. “To me, Trump’s purge is only about vindictiveness. He wants to strike out at and defeat the people who have dared to criticize him.”
Other presidents have been incensed by wayward members of their parties, but few attempted what Roosevelt did and what Mr. Trump is threatening. Karl Rove, deputy chief of staff to President George W. Bush, at times grew livid at Republicans who defied the White House. But he said the idea of challenging them in primaries was anathema.
Roosevelt’s experience showed the dangers of isolation in the White House, said Mr. Rove, who has sharply criticized Mr. Bannon’s efforts. “The lesson is it’s better to try to influence by encouragement than by opposition,” he said. “It’s important to keep focused on the main things people want you to keep focused on — what are the big issues of the day? And don’t let your personal pique guide your political actions.” (Mr. Bannon said he would not reply because it would be “punching down.”)
Unlike Mr. Trump, with his historically low poll ratings, Roosevelt was broadly popular at the time. He swept to re-election in 1936 with 61 percent of the vote, winning all but two states in one of the biggest landslides in American history, and his approval ratings remained high. While Mr. Trump’s Republicans can afford to lose only two votes in the Senate, Roosevelt’s Democrats enjoyed large majorities in Congress.
But Roosevelt grew angry at resistance from Democrats to additional domestic programs and repeated Supreme Court rulings overturning parts of the New Deal. The confrontation came to a head when he sought to pack the Supreme Court by adding as many as six more justices to seize control of the bench, an idea that provoked fierce opposition in both parties and ultimately collapsed.
Harry Hopkins, Roosevelt’s confidant, railed against Democrats “who tricked the voters by wearing our insignia only to turn against us as soon as they got in office.” Roosevelt was so angry that his “resentment crystallized into the desire to crush all who conspired against the throne,” said George Creel, a journalist and critic at the time. So Roosevelt put together a team to organize a campaign against the conservative Democrats. The newspapers called it the “elimination committee” and labeled the campaign Roosevelt’s “purge,” a reference to Stalin’s terror in the Soviet Union.
Advisers like Frances Perkins feared it was “reckless” but could not talk him out of it. On June 24, 1938, Roosevelt announced during a fireside chat that he had a responsibility to carry out the 1936 platform and therefore would oppose the election of “outspoken reactionaries” and hypocrites “who say ‘yes’ to a progressive objective, but who also find some reason to oppose any specific proposal designed to gain that objective.”
He took on conservatives like Senators Walter F. George of Georgia, Ellison D. Smith of South Carolina, Millard E. Tydings of Maryland and Guy M. Gillette of Iowa. Mr. Smith, a fierce segregationist known as “Cotton Ed,” despised Roosevelt and referred to the New Deal as the “Jackass Age.” But Mr. Smith and the others won anyway. Roosevelt managed to take out only one rival in the House. Amid the Democratic discord and the aftermath of a recession, Republicans swept to victory in the fall, picking up eight Senate seats and 81 House seats by Ms. Dunn’s count.
“Unfortunately, his hubris overwhelmed his normally impeccable political instincts,” said Paul Sparrow, director of the Franklin D. Roosevelt Presidential Library and Museum. But it had unanticipated benefits. “The good news for history,” he said, “is that this embarrassment taught him an important lesson: Don’t get too far out in front of the American voter, a lesson he applied just two years later as he carefully laid the groundwork for America’s entry into World War II.”
Indeed, Ms. Dunn said some of the same conservative Democrats who survived Roosevelt’s purge ultimately became his strongest allies during the buildup to the war. Mr. Tydings backed Roosevelt’s compulsory universal military service, and Mr. George played a key role in passing the Lend-Lease Act to supply Britain and other countries with military aid.
“So,” Ms. Dunn said, “I guess the lesson is, be careful what you wish for.”