The relationship between the United States and United Kingdom hasn’t seemed so “special” in recent years. In fact, that characterization of the bond between London and Washington waned in 2016, when then-candidate Donald Trump referred to himself as “Mr. Brexit” even though previous Prime Minister David Cameron campaigned to remain in the European Union.

Once elected, President Donald Trump didn’t mesh well with Cameron’s successor, Theresa May, a “remainer” who dutifully declared “Brexit means Brexit” once her Conservative Party chose her as prime minister. But May’s Brexit plan repeatedly stalled in Parliament, leading her to resign.

The special relationship was rocked further by leaked classified cables from Kim Darroch, Britain’s ambassador to the United States, who characterized the Trump administration as “clumsy and inept.” After being targeted by Trump on Twitter (where else?), Darroch resigned.

Last week, a plebiscite of about 160,000 Conservative Party members chose Boris Johnson as the U.K.’s new prime minister. Johnson’s Tories have a tenuous parliamentary majority, and Johnson could face a no-confidence vote or even a general election if his Brexit “do or die” pledge means a “no deal” exit by the auspicious E.U. deadline of Oct. 31 — Halloween.

And a no-deal Brexit could be a big deal for U.K. unity. The potential of a “hard border” between Northern Ireland and the Republic of Ireland could set back the steady success of the Good Friday peace agreement that finally quieted the Troubles. Scottish independence could be at play again, too.

Johnson has hopes that he can convince the E.U. to cut him a better deal than they did May, or that he can convince Parliament to pass a plan like the previous versions they repeatedly rejected (both scenarios are unlikely). He also hopes for an eventual bilateral trade agreement with the U.S. — a prospect Trump has touted, too. But formal negotiations couldn’t commence until Brexit is complete. And like other trade pacts, that is much easier said than done for a process that usually takes years, not months.

Regarding any potential negotiations, “Trump is in a stronger negotiating position and will likely drive a hard bargain, which could require the U.K. to make some difficult decisions on controversial issues,” Amanda Sloat, a senior fellow at the Brookings Institution’s Center on the U.S. and Europe, told an editorial writer in an e-mail exchange.

In general, the president has prodded Johnson along, even calling him “the Britain Trump.” While it’s welcome to have the U.S. and U.K. leaders more cohesive, it’s important for Trump to not let an improved special relationship erode relations with E.U. nations at odds with Britain over Brexit.

British public-opinion polls reflect tepid support for the new prime minister. And many don’t think highly of the U.S. president, either.

“Trump is almost as divisive in Britain as he is in the United States,” John Roberts, a British-based fellow at the Atlantic Council, told an editorial writer. However long they last, the Trump and Johnson eras will eventually end.

But for the good of each nation, the special relationship between the U.S. and the U.K. — as well as Europe — must endure.