British Prime Minister Theresa May says she will resign next month over her inability to get a Brexit deal approved by parliament, and a former aide to the late Prime Minister Margaret Thatcher says new leadership will likely mean a clean exit for the country from the European Union.

May took office in 2016 in the wake of British voters approving Brexit.  Prime Minister David Cameron immediately stepped down after vigorously leading the effort to defeat Brexit.  Cameron said a supporter should lead the effort to leave the EU, but May's approach led to one failure after another.

"Theresa May has failed to deliver on Brexit.  She has also been seen within the conservative party as incredibly weak in her dealings with the European Union," said Nile Gardiner, director of the Margaret Thatcher Center for Freedom at the Heritage Foundation and a former assistant to Thatcher after she left office.

May spearheaded two failed attempts for a Brexit deal to clear the House of Commons.  It was clear her third attempt would fare no better.   Gardiner says the prime minister suffered loss after loss because she kept pursuing the wrong priorities.

"The agreement between the British government and the European Union is in many ways a very bad deal.  It doesn't guarantee that Britain is able to exit the EU Customs Union.  What that means is that Britain would not be able to sign its own free trade agreements.  It would be subject to EU tariffs   It would be, in essence, still a part of the European Union," said Gardiner.

"In many ways, Theresa Mayu is the antithesis of Margaret Thatcher.  She displayed no real courage in the negotiations with the European Union.  She did not stand up to the EU.  She caved in to all of their demands.  It was a disastrous handling of Brexit and it's time now for a new prime minister who actually fully believes in Brexit and is going to deliver on it," added Gardiner.

Conservative Party members already raised two no-confidence votes against May, but she survived both challenges.  Gardiner believes efforts to change the party rules to remove May, coupled with a looming disaster in EU parliamentary elections, played a significant role in May's decision to resign now.

"I think she jumped before she was really pushed out," said Gardiner.

Former London Mayor Boris Johnson is seen as the front-runner to become party leader but Gardiner expects 10-15 people to run for the position.  And he's confident that whoever emerges will be serious about implementing the Brexit that voters approved three years ago.

"The majority of leading contenders to replace Theresa May are Brexiteers.  They're people who voted for Brexit and believe in Brexit and who are prepared to implement a no-deal Brexit as well," said Gardiner.

Listen to the full podcast to hear Gardiner explain the specific Brexit idea that sealed May's doom within her own party and how the leadership change will likely impact U.S.-British relations for the better.