May called the election on April 18, confident she would gain a commanding majority to strengthen her hand in the talks to steer Britain out of the EU.
She began with a mantra, tirelessly repeated, that she offered "strong and stable leadership" over Labour leader Jeremy Corbyn, who is perceived by many voters as weaker and less competent.
But, to the surprise of many, control of the agenda slipped away from her and Corbyn closed the gap.
On Thursday voters will determine whether May, if she wins, will start a new chapter as a sure-footed leader or, as one commentator has suggested, a "blowhard who collapses at the first sign of gunfire."
On the campaign trail, May reversed course on how much elderly people should pay for their care -- a policy that alarmed the house-owning middle classes on whom the Conservatives depend for their vote.
Her U-turn also shone a light on May's habit of relying on a few trusted advisors, which saw even cabinet ministers excluded from discussion over parts of the Tory manifesto.
And after bloody jihadist attacks shook London and Manchester, May came under cold scrutiny for her six-year record as interior minister, when she oversaw hefty cuts in police payrolls.
Labour leader Jeremy Corbyn gained ground, torching Tory hopes of transforming her slender 17-seat advantage in the House of Commons into a triple-digit majority.
Personality
But May's personality, as well as her tactics, has been part of her problem, say analysts.
The election campaign exposed an awkward manner with the public, a reliance on soundbites and a seeming preference for stage-managed campaign events rather than head-to-head debate.
In a rare unscripted encounter that was filmed and went viral, May trotted out bland campaign slogans as a woman voter angrily confronted her over welfare cuts.
In a country divided along lines of class, wealth and regional affiliation, the 60-year-old Conservative mirrors the image of the white, educated upper-middle classes of southeast England in which she grew up.
May has shrewdly sought to turn this otherwise unremarkable background into an advantage, making a discreet parallel with Margaret Thatcher, Britain's first woman prime minister and Conservative heroine.
Like Thatcher, she seeks to project an image of herself as pragmatic and steadfast, rather than flashy and unstable.
May similarly dresses conservatively -- her most talked-about fashion preference is for fake leopard-skin shoes with flat heels and for bobbed hair.
And like Thatcher, she has cultivated a tough, no-nonsense image.
She relishes the label of "a bloody difficult woman" once placed upon her by a colleague and raised eyebrows last week by saying she had had "the balls" to call a snap election.
She and her husband Phillip had tried to have children but failed, an issue that she admitted had caused sadness, but "you accept the hand that life deals you."
May grew up in the prosperous county of Oxfordshire, with a father who was a Church of England vicar and her mother who was an enthusiastic member of the Conservative Party.
She studied geography at Oxford University before working in the financial sector, firstly at the Bank of England and then as a consultant.
After a period as a local councillor in London, she entered national politics, becoming MP for the prosperous constituency of Maidenhead, in the London commuter belt, in 1997.
She served as home secretary -- interior minister -- under David Cameron.
Brexit chance
In the June 2016 referendum on EU membership, she supported, although with little visible enthusiasm, Cameron's pitch to remain.
In the chaos that followed victory for the Leave vote, Cameron quit and May cannily stepped into the void.
She put herself forward as the safest pair of hands for dealing with the business of Brexit, endorsing "good, solid Conservatism" that defended the interests of all, and not just the privileged.
jpegMpeg4-1280x720Perhaps the most telling illustration of May was when she was asked to describe the naughtiest thing she had ever done.
"Oh goodness me. Um. Well, I suppose –- gosh. Do you know, I'm not quite sure," May prevaricated, before admitting that she and her friend had once run through a field of wheat, angering farmers.
Her admission "disappointed for its undeniable lameness," said the leftwing daily The Guardian. Social media was similarly scathing: "The Thatcher in the Rye," was a comment on Twitter.
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