Pretty much every element of Trump’s diplomacy with North Korea.

Obama set off Republicans and his Democratic rival Hillary Clinton during his first presidential campaign by pledging to meet unconditionally with the leaders of adversarial countries. His political opponents later pilloried him for appeasing America’s authoritarian enemies in seeking to constrain Iran’s nuclear program and reconcile with Cuba.

Imagine the uproar if Obama had held a splashy summit with Kim Jong Un in return for no substantive concessions on North Korea’s nuclear-weapons arsenal—let alone if he had done that three times, as Trump has, including the first presidential foray into North Korean territory. What if Obama had gushed about how he “fell in love” with North Korea’s dictator? Or unabashedly taken the totalitarian leader’s side in disputes with a former American vice president and the president’s own national security adviser? Or absolved Kim of responsibility for the death of an American college student in North Korean captivity? Or castigated the CIA for cultivating Kim’s half brother as an intelligence asset? Or, while we’re at it, saluted a North Korean general? (See: the various controversies surrounding Obama’s bows to U.S. partners such as the Saudi king and Japanese emperor.)

Trump’s supporters tend to explain away this behavior as the unsavory means by which the president hopes to achieve a worthy objective: a nuclear deal with North Korea, which has eluded his predecessors. They note that Trump has held firm on severe North Korean sanctions. “For 30 years, they’ve been trying to pound a round peg in a square hole,” the Republican Senator James Risch once told me, regarding the history of U.S. talks with Pyongyang. “Things need to be done differently.” If nothing else, even as Trump has worked to erase nearly every aspect of Obama’s foreign-policy record, the two presidents have fashioned a joint legacy: shattering the long-standing bipartisan American taboo of presidents directly engaging with their foes.