Twenty-three years ago Margaret Thatcher resigned as prime minster of Great Britain. Since then, no woman has been a serious contender to lead the Conservative Party. That may be about to change. Britain’s next general election is scheduled for May 2015, and polls indicate Conservative Prime Minister David Cameron is likely to lose. Speculation about who would succeed him as party leader centers on Boris Johnson, the flamboyant mayor of London. But another prospect should not be overlooked: Theresa May, named by BBC Radio as the second most powerful woman in the country—after only Queen Elizabeth II.

Right now, May is one of several “Not Boris” possibilities, but at least one person rates her chances highly. During prime minister’s question time earlier this year, Ed Miliband, leader of the Labour Party, said to Cameron, “I’m looking forward to facing her when you’re in the opposition.” Some MPs laughed, but May only gave her signature steely gaze.

Cameron’s problems are deeply rooted. He has never been a perfect fit for the Conservative Party’s traditional base, which still blames him for not winning the 2010 election outright, necessitating a coalition government with the Liberal Democrats. Cameron’s push to legalize gay marriage further infuriated much of the grassroots.

For now Cameron looks unlikely to meet Mrs. Thatcher’s fate, toppled by a revolt from within the party. But if the Conservatives continue to struggle in the polls and preform poorly in other contests ahead of the next general election, that could change. And if Cameron loses the election, his departure as party leader as well as prime minister is assured.

As home secretary in Cameron’s cabinet, May runs the department that handles policing, crime, immigration, and counter-terrorism. In recent times, the office has been seen as something of a poisoned chalice. But May has done well with it. “When Labour was in office, they’d have a new Home Secretary every two years. She’s held the post three-and-a-half years, and there have been no major scandals. That is a great credit to her,” says Matthew Elliott, who founded the Taxpayers’ Alliance and who is sometimes called “the Grover Norquist of the UK.”

Part of May’s success is circumstantial. When the economy is doing well, the British media closely scrutinizes the types of policies the home secretary handles. Since lately all the attention has focused on the economic crisis, May has had an easier time of it.

“She sees it as a standing post where she can show herself as a competent manger—a figure like Angela Merkel. Sure, she’s gray and lacks humor, but she is competent,” says Elliott.

The German Chancellor, who led her party to a decisive re-election victory in September, is widely admired in Great Britain. Like May, Merkel rose slowly but steadily. And the two women come from similar family backgrounds. May’s father was a Church of England priest; Merkel’s father was a pastor and theologian in Germany. Both women are childless, leaving them free to work long hours.

In interviews, May has indicated that she decided on a career in politics at a young age. She was a member of Oxford University’s Conservative Association during her undergraduate years. She met her husband, Philip, at a Tory student party. He works as a banker in London—and networks tirelessly on behalf of his wife’s career.

May’s rise through the ranks has been anything but fast. She was elected to local government in 1986 and to Parliament in 1997. Along the way, she made it her business to get other women elected. She helped develop the “A-list” system of candidate selection that dramatically increased the number of Conservative women and minority MPs. She also co-founded Women2Win, a group that supports Conservative women for office. A byproduct of these efforts is that a lot of MPs owe her favors, which could come in handy because, under Tory rules, it’s the MPs who choose their new leader.

The Guardian’s Gaby Hinsliffe recently summed up the 57-year-old home secretary’s career:

Once dismissed as an over-promoted token woman, she has held her own in one of the toughest jobs in cabinet, combining classic conservative values of frugality, propriety and stoicism with thoroughly modern instincts.

Feminist causes she was once mocked for championing are now mainstream Tory thinking, and her legacy includes two things which arguably shaped the modern party … the A-list scheme for candidate selection, which gave birth to several rising stars, and the infamous “nasty party” speech, which made Tories take a long, hard look in the mirror.

That moment of reflection came in 2002, when May served as chairman of the Conservative Party. At the annual party conference that year, she gave the now infamous address in which she said, “Twice we went to the country unchanged, unrepentant, just plain unattractive. And twice we got slaughtered. You know what some people call us? The nasty party.” The phrase has since entered the British political lexicon.

At the time her speech created an uproar. Will those words come back to haunt her if she seeks the leadership? “It will be brought up by supporters of her opponent in a hypothetical leadership race. But most people will recognize that it was a long time ago,” says Elliott. “People realize that’s a mentality that all the party’s leadership shared. It should be considered as part of a wider analysis of where the Conservative Party was at that time.”

And where is the Conservative Party today? Cameron is dogged in the polls by—among other things—the rise of the UK Independence Party (UKIP), which is aggressively courting Tory traditionalists tired of Cameron’s progressivism. UKIP has never done well in a British general election, but the party seems set to win perhaps 25 percent of the vote in the EU election scheduled for May 2014. The bounce from that could well see them winning 5-7 percent of the national vote in 2015—probably enough to deny Cameron a parliamentary majority.

That threat, atop of all the other discontents, has Conservatives already contemplating life after Cameron. Boris Johnson is the most popular politician in Great Britain, and many Tories dream of turning to him for rescue. “Boris has election-winning form. He’s just won two successive elections as London Mayor. London is a Labour city. He is also very popular with the Conservative grassroots who pack in whenever he speaks at a party conference,” says Elliott.

But Johnson is currently ineligible to become prime minister because he is not an MP. British law permits him to hold two offices concurrently, but he has pledged to serve only as mayor until his term ends in 2016, by which time the Conservatives may already have lost; if Johnson became leader then he would face five years of being an opposition leader—a difficult job with a lot of slog and very little glory.

Johnson is a star who loves the limelight. He might prefer to sit out the next Tory leadership race—sure to be a bitter affair, full of recrimination—only to swoop in and become leader closer to 2020, overthrowing whoever held the post after Cameron. There is some ignominious precedent for this: Iain Duncan Smith led the Conservative Party between 2001 and 2003 but was replaced before he ever got to contest an election.

If Johnson does not run at the next opportunity, the likely prime contenders are May, who has supported gay marriage and would represent the party’s “modernization” wing, and another candidate who would stand for the party’s traditional base. That could be Michael Gove, the education secretary, who is very popular with the grassroots. Reports of verbal spats between Gove and May during cabinet meetings not infrequently reach the media.  Web issue image

May is not without some appeal to the right, however, and has come under fire from the left for proposing more restrictive policies to crub illegal immigration. She told BBC Radio 4: “Most people will say it can’t be fair for people who have no right to be here in the UK to continue to exist as everybody else does with bank accounts, with driving licenses and with access to rented accommodation. We are going to be changing that because we don’t think that is fair.”

Could she find the balance between outreach and the base that has eluded Cameron? Even if not, should the next Tory leadership contest come down to perseverance rather than charisma, she may have an edge. Theresa May’s career, much like Angela Merkel’s, has taught her that slow and steady wins the race.

Emma Elliot Freire is an American writer based in England.