With U.K. Prime Minister Boris Johnson stepping down as in the fall, a crowded list of candidates is waiting to potentially take his place.

"What’s interesting about the current situation is that there is no obvious heir apparent to take over from Boris," Alan Mendoza, the co-founder and executive director of The Henry Jackson Society, told Fox News Thursday.

With the Conservative Party still being in control of the U.K. government after winning a majority during the 2019 election, the next prime minister will be a member of the party. But what member of the party will take over for Johnson is still up for debate, with candidates such as former Chancellor Rishi Sunak, Trade Minister Penny Mordaunt, and Defense Secretary Ben Wallace seen as potential favorites to be the country's next leader.

Betting markets currently favor Wallace, whose leadership of the British response during Russia's invasion of Ukraine has gained praise, according to odds released by Sky Bet. Sky Bet views Sunak as the second most likely candidate, while Mordaunt, checks in at third on the betting site.

UK PRIME MINISTER BORIS JOHNSON ANNOUNCES RESIGNATION

UK Prime Minister Boris Johnson announces his resignation in London July 7, 2022

British Prime Minister Boris Johnson (Reuters/Peter Nicholls)

Other betting sites have Wallace in third place behind Sunak and Mordaunt. Sunak, who resigned from Johnson's cabinet earlier this week, is viewed as a potentially fiscally responsible leader who can get the country's finances on track, while Mordaunt is a rising figure in the party who flipped a constituency held by the Labour Party between 1997 and 2010 and has used her background as a pitch to appeal to the country's working class voters.

Polling shows a similar picture to the bettering markets, with one survey showing Wallace leading the pack as the preference of Conservative Party members. Mordaunt and Sunak follow closely behind, while long shots such as Liz Truss, Jeremy Hunt, and Nadhim Zahawi all garner some support.

"No successor polls anywhere show the kind of lead he [Johnson] had at the last leadership election, either internally within the party or externally in the country," Mendoza said.

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The choice will be a critical one for the Conservative Party, with speculation growing that a general election could be called as soon as this year. While betting odds believe that is unlikely to happen until 2023, Mendoza said the next leader will be looking to present a vision to voters.

"The party itself will be looking for competence, stability and a clear vision from the next leader rather than ideology and if the winner can deliver this they have a very good chance of also winning the next general election." he said.