INTERNATIONAL REACTION to Joe Biden’s presidential election victory provides a useful map of the state of U.S. alliances — and of democracy — around the world. At one extreme, the world’s leading democracies, and closest U.S. allies, were quick to congratulate Mr. Biden on his victory — despite the refusal of President Trump to concede. Britain, France, Germany, Canada, Japan, India, South Korea and Italy all appeared to be doing their part to help the United States avoid a political crisis by quickly recognizing the president-elect.

At the other extreme were Russia and China, which on Monday were still declining to accept the results, citing Mr. Trump’s legal challenges. Especially in the case of the regime of Vladimir Putin — which, according to the CIA, attempted to aid Mr. Trump’s reelection — that looked like an effort to help him discredit the result. No doubt Beijing, as well as Moscow, welcomes Mr. Trump’s effort to tarnish the U.S. political system, which may make their autocratic models look more attractive by comparison.

In the middle of global reactions were a group of nations that closely allied themselves with Mr. Trump. In the Middle East, Saudi Arabia, Israel and the United Arab Emirates were slow to congratulate Mr. Biden, but eventually did so, perhaps because they recognize their security depends on continued U.S. support. Then there were the governments that share Mr. Trump’s autocratic populism, such as Poland, Hungary, Turkey, Mexico and Brazil. As of Monday, the last three had yet to recognize the U.S. election outcome, while Poland’s president tried to split the difference, offering congratulations to Mr. Biden “as we await . . . the Electoral College.”

Thanks to Mr. Trump, Mr. Biden may be perceived, at least initially, as less legitimate than previous U.S. presidents in some parts of the world. But the relative good news is that he will have the opportunity to quickly restore damaged ties with key U.S. partners. Foreign Minister Heiko Maas of Germany, one of the allies most abused by Mr. Trump, proposed a “New Deal” in relations, and said Berlin would approach the Biden administration with “concrete proposals on how we can close ranks as a transatlantic community” on challenges such as China, climate protection and the covid-19 pandemic.

What Mr. Maas and other allied leaders don’t say aloud is that they hope Mr. Biden, through his election and through his policies, will help turn back the tide of nationalist populism that has risen in countries throughout the West. The president-elect has pledged to hold a summit of democracies during his first year in office that would “honestly confront nations that are backsliding.” Hungary and Poland are likely to be high on that list; Mr. Biden in the past has described them as incipient “totalitarian regimes.”

At best, the new U.S. president can give new momentum to the global cause of liberal democracy at a time when it badly needs it. That will mean bolstering U.S. democratic institutions against the threat of another would-be autocrat such as Mr. Trump — and using U.S. leverage to support democratic movements in allied nations as well as adversaries.

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