Who will succeed Boris Johnson as Britain's next prime minister?

British Prime Minister Boris Johnson’s resignation will trigger a Conservative Party leadership contest to select the nation’s next leader.

While there is no clear frontrunner for the U.K's top job, several names already have emerged as possible successors to Johnson – a brash, colorful politician whose turn in leadership was marred by scandal and ethical lapses.

The latest

• Johnson quits: Johnson announced on Thursday that he would resign after a full-throated revolt among his erstwhile Conservative Party allies. Johnson said he will remain in office until his successor is chosen.

• What’s about to happen: Johnson said the process to select a successor would start immediately and a timetable would be announced next week.

• How does it work? British voters elect a party, not a leader. Johnson's exit will lead to an internal Conservative Party election to determine the next prime minister.

• Backing his replacement: Johnson vowed to support his successor and predicted another leader would emerge who is "equally committed to taking this country forward through tough times.” One who won't is British Defense Secretary Ben Wallace who said Saturday he would not vie for the job.

Who are the top contenders?

Though there is no early favorite, a clutch of Conservative political contenders has surfaced as the political jockeying gets underway.

Here's a close look at some of the possible candidates:

Penny Mordaunt

Penny Mordaunt, 49, is regarded by many as the frontrunner to succeed Johnson. A Conservative, she has been a member of Parliament since 2010 and has served as trade minister since last September. Mordaunt has held various posts in Conservative governments, including a stint as minister for local government, and she was the first woman named armed forces minister. She was one of the leaders behind the “Brexit” referendum approved by voters in 2016, which led to Britain's separation from the EU.

Mordaunt is a reservist in the Royal Navy and the daughter of a former paratrooper. If named as Johnson’s successor, she would be only the third woman to become prime minister, behind Margaret Thatcher and Theresa May.

Liz Truss

Liz Truss, 46, has been a member of Parliament since 2010 and currently serves as the British foreign secretary. She has held various other positions in government, including secretary of state for international trade and secretary of state for environment, food and rural affairs.

Popular and ambitious, Truss voted for Britain to remain in the EU but has since had a change of heart. She is now the lead negotiator with the EU in talks to work out post-Brexit issues over Northern Ireland. Her supporters have coined the phrase “In Liz we Truss.”

Rishi Sunak

Rishi Sunak, 42, was the U.K.’s chief financial minister until Tuesday when the high-ranking minister abandoned Johnson and resigned from his role, asserting the British government is not being run “properly, competently or seriously.”

Sunak assumed the role of chancellor of the Exchequer in February 2020, just as the COVID-19 pandemic began to pick up steam. He led the U.K.’s pandemic aid rollout, which led many to view him favorably and as a likely successor to Johnson. However, the former minister’s popularity waned amid a series of controversies, including his wife’s non-domestic tax status and a fine for partaking in an illegal, pandemic-era Downing Street party, according to Bloomberg.

Jeremy Hunt

Jeremy Hunt, 55, served as Britain’s health secretary from 2012 to 2018. He faced Johnson in the Conservative Party's 2019 leadership election and lost by a landslide.

Tim Bale, politics professor at  Queen Mary University of London, described Hunt as  the "Mitt Romney of British politics" in 2019, a reference to the Utah senator known for his professionalism and lack of political charisma. Hunt has painted himself as a toned-down alternative to Johnson, often speaking publicly about Johnson’s purported mistakes.

Who won't run

British Defense Secretary Ben Wallace, 52, was among the favorites to succeed Johnson.  But on Saturday, he announced on Twitter that he will not be entering the contest for prime minister.

"It has not been an easy choice to make, but my focus is on my current job and keeping this great country safe," he wrote.

Wallace assumed his role as defense secretary in July 2019 but entered politics two decades prior as a member of the Scottish Parliament, according to his official bio. He's currently the U.K.'s longest serving security minister and the Member of Parliament for the Wyre and Preston North county constituency. Before that, he was an army captain.

Why it matters

• The U.S. and the U.K. are loyal allies and have what is often referred to as a “special relationship.” Johnson has been among the most reliable and vocal supporters of President Joe Biden's efforts to isolate Russia after its unprovoked invasion of Ukraine.

• No matter who is chosen, the new prime minister is unlikely to have a major impact on Britain's relationship with the U.S., its closest ally.

• The U.S.-U.K. alliance, which encompasses national security, defense, intelligence sharing, trade and close cultural ties, enjoys bipartisan support.

• Nor is there likely to be any change to Britain's support for Ukraine in its unprovoked war with Russia. Apart from the U.S., Britain has contributed the most heavy weaponry to Ukraine.

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This article originally appeared on USA TODAY: Boris Johnson's successor: Who will be Britain's next prime minister?