London — Former London Mayor Boris Johnson has been chosen by his party to become Britain's next prime minister. He will replace Theresa May, who was forced to resign amid a bitter feud in the U.K. -- and within both her and Johnson's Conservative Party -- over Britain's exit from the European Union.

As CBS News correspondent Charlie D'Agata reports, the new leader of America's closest ally is one of Great Britain's most prominent figures, and probably a familiar face to many Americans.

By a quirk of British politics, Johnson was not elected by the general public but instead chosen to lead by about 160,000 registered Conservative Party members. He won with 92,153 votes to rival Jeremy Hunt's 46,656 — a margin of almost two to one.

Boris Johnson speaks after being announced as Britain's next prime minister at The Queen Elizabeth II Centre in London, Britain, on Tue., July 23, 2019. Reuters

The new prime minister will officially take office on Wednesday, when May formally resigns the post. Johnson thanked his opponent in the leadership contest, Hunt, and May in remarks to gathered party members in London after the results of the election were announced Tuesday.

Get Breaking News Delivered to Your Inbox

Johnson vowed to "unite this amazing country and take it forward" while pulling it out of the European Union to "take advantage of all the opportunities that it (Brexit) can bring."

He replaces the beleaguered May, who was forced out after repeatedly failing to deliver a deal for Britain to leave the EU that the British Parliament could agree on.

What's it mean for U.S. relations?

Despite once accusing President Trump of "stupefying ignorance" and "being unfit for office" for suggesting there were parts of London so violent they were "no-go" areas even for police, Johnson has recently softened his tone considerably.

Notably, he kept quiet about President Trump's description of now-former British Ambassador Kim Darroch as "wacky" and "very stupid guy" after leaked diplomatic cables revealed Sir Darroch's low opinion of the current American administration.

Jeremy Hunt, Johnson's challenger to lead the Conservative Party whose loss was confirmed on Tuesday, was more forthright in condemning Mr. Trump's stinging personal attack on Darroch, which forced the ambassador to resign.

Johnson's brand of bombast, brashness and bad hair has earned him a reputation of something of a political renegade in the U.K. But he has repeatedly stressed the importance of having a close relationship with the United States.

President Trump welcomed Johnson's victory, predicting in a tweet early Tuesday that the new prime minister would "be great!"

Congratulations to Boris Johnson on becoming the new Prime Minister of the United Kingdom. He will be great! — Donald J. Trump (@realDonaldTrump) July 23, 2019

The change of leadership comes at a critical time for U.S.-U.K. relations, with a British tanker currently in the hands of the Iranian military and both America and Britain boosting their military presence in the Persian Gulf.

As a reminder of the potential geopolitical tinderbox he will inherit, Iran's Foreign Minister Javad Zarif sent a tweet addressing Johnson on Tuesday, congratulating him and adding a reiteration of Tehran's view that the seizure of an Iranian tanker off Gibraltar, which preceded the seizure of Britain's tanker by Iran, amounts to "piracy, pure & simple."

"Iran does not seek confrontation," Zarif said. "But we have 1500 miles of Persian Gulf coastline.These are our waters & we will protect them."

The May govt's seizure of Iranian oil at behest of US is piracy, pure & simple. I congratulate my former counterpart, @BorisJohnson on becoming UK PM. Iran does not seek confrontation. But we have 1500 miles of Persian Gulf coastline.These are our waters & we will protect them pic.twitter.com/svEqmEHQBM — Javad Zarif (@JZarif) July 23, 2019

The U.K. is working with other European nations to move more military vessels to the Gulf region to secure the vital shipping channels in and out of the body of water, but thus far most EU nations have resisted the Trump administration's call for a "flotilla" specifically operating with a mandate to keep Iranian vessels in check.

Boris and Brexit



Johnson will take the reins of power in the U.K. just ahead of a crucial split in the road for Britain's political future.

Britain is currently scheduled to leave the European Union on Oct. 31 — per the wishes of a majority in Britain's four countries (England, Scotland, Wales and Northern Ireland) expressed in a 2016 public referendum.

Johnson has been a hardline "Brexiteer" since before the referendum, pushing for the U.K. to exit the trade and customs bloc it helped found more than half a century ago. He has vowed to deliver that exit Oct. 31, with or without a deal in place with the EU to lay out new rules for trade and travel to replace the web of regulations built up over decades among the 28 member states.

Economists and politicians have warned that such a "no-deal" divorce could wallop Britain's economy, as the free-trade among neighbors and dozens of trade deals negotiated with the wider world by the bloc would suddenly be replaced for the U.K. by World Trade Organization rules.

That would require Britain, only the EU's second largest economy, to negotiate new, unilateral trade deals with all of its trading partners across the globe, including the U.S. It would have to do so from a much weaker position, without the collective bargaining power of the rest of Europe behind it.

Dire warnings of bottlenecks at ports and airports as new customs and travel rules are put in place, and even possible shortages of food and medicine, have been issued over the "no-deal" Brexit scenario.

But Parliament could try to stop Johnson letting it get to that point. Many members of his own Conservative Party, and crucially a majority of all Members of Parliament, do not believe the U.K. should crash out of the EU without a deal in place.

If Johnson lasts long enough in the office (he could be ousted at any time with a vote of no confidence leading to a new national election) to try and force a no-deal Brexit, Parliamentarians have been working behind the scenes for weeks on a way to stop him — and the way Britain's democracy works, they may well be able to do it.

If Parliament were to block a no-deal Brexit, it's unclear when, how or even if Britain's exit from the European Union might actually happen.

As has been the case with Brexit since the day after the referendum, regardless of who inhabits the Prime Minister's official residence at 10 Downing Street, nothing is certain.