The Conservative MP overplayed her hand

Who can blame U.K. Prime Minister Theresa May for calling an election now, as her own Conservative Party mandarins have been urging?

Her party enjoys a 21-percentage-point lead in the polls. The opposition Labour Party is weak and divided, and the British economy has yet to register the expected wobbles in the wake of last year's vote to leave the European Union. What better time to crush the opposition and beef up the Conservatives' 17-seat majority in Parliament?

Yet May's decision is as strategically flawed as it is tactically clever.

First, she risks losing credibility. Having promised not to get distracted by an election campaign before the current term expires in 2020 — working out the nuts and bolts of Brexit, after all, is hard work — she's now reversed herself. Voters are accustomed to politicians who go back on their word, so she may be forgiven. But the volte-face won't be forgotten. Voters will wonder whether other pledges will be similarly rethought if there's political advantage to be gained.

Second, May risks offending the cherished British notion of fair play. She has fired the start gun before her competition has even rolled out of bed. She'll win, but she risks sparking a nascent sympathy vote for the first underdog to show some signs of life.

It's almost cruel to hold an election now given the hapless state of Labour. At the start of the year, the country's oldest think tank, the Fabian Society, declared Labour unelectable, despite having helped to found the party and long being closely associated with its causes. The threat of Britain becoming a one-party state is real enough that the Economist put the prospect on the cover.

The U.K. Independence Party has an unrecognizable leader and no clear mission. The one-time Conservative coalition partner, Britain's Liberal Democratic Party, is down to nine seats. It is, on the back of strong support for remaining in the E.U., registering a pulse again, but it's a long way from being competition-ready. Even the fiery Scottish Nationalists look to have miscalculated in their call for a new independence referendum before negotiations with the E.U. about the terms of the U.K.'s departure are even truly underway.

The prime minister pointed a finger at the opposition parties (and by extension, those in her own party who are dragging their feet on Brexit). She said division jeopardized the chances of getting a good Brexit deal and accused her detractors, as she has in the past, of playing political games.

In fact, the entire case for new elections was couched in terms reminiscent of the way Winston Churchill rallied the country for a war of survival.

"There should be unity here in Westminster," May said. "Instead there is division. The country should be coming together, but Westminster is not." The upshot: Those who aren't with me are against me, and those who are against me are against the country.

Brexit is historic and complicated and consequential. But it isn't an existential battle against an external foe. It isn't disloyal to question the government's strategy or oppose it. The furniture in the House of Commons is arranged in two facing rows precisely because debate and challenge are central to democracy.

May has fostered the perception that she is above the pettiness of party machinations; that sometimes she is even the only adult in the room. She didn't vote for Brexit, but has vowed to carry it out. She casts herself as the master of detail, drawing up lists and working through them; she does policy, not politics.