It looks like a political game-changer in Britain.

Boris Johnson, the Conservative mayor of London, has announced that he will run for a seat in Parliament in the election scheduled for May 2015. Johnson went on to disparage his chances of being adopted as a Conservative candidate by some constituencies, but my sense is that a lot of local Conservative parties will be itching to have him as their candidate, and indeed the Telegraph quotes the party leader in the open and safely Conservative London seat, picturesquely named Uxbridge and South Ruislip, as welcoming Johnson.

Most Americans haven’t had much glimpse of Johnson except in his role in welcoming the 2012 Olympics to London — and belittling “a guy called Mitt Romney” for expressing doubts about whether London was fully prepared to host the games. This was politically shrewd. Most Brits — including many though not all in high positions in the Conservative Party — have little use for Republicans. If you want to see more examples of Johnson’s political shrewdness, take a look at his Telegraph columns, in which he frequently lavishes praise on Prime Minister David Cameron — or does he?

There has long been speculation that if Conservatives lose the 2015 election, Johnson will run to succeed Cameron as leader of the party. That would displace Cameron’s close ally and longtime friend, Chancellor of the Exchequer George Osborne. (Actually, all three were in the same social circle at Oxford not so long ago.) But more to the point, I think, is Telegraph columnist Tim Stanley’s suggestion that Johnson will be a great asset to the party in 2015.

It’s a little awkward that Johnson’s second term as mayor extends to May 2016; if elected to the House of Commons, he would have to serve there as well as in city hall. Johnson’s effervescent personality and effrontery, Stanley speculates plausibly, will undercut the United Kingdom Independence Party’s leader Nigel Farage, who is typically interviewed with a cigarette in one hand and a pint of ale in the other. Johnson’s tousled hair, his confidently flamboyant way of speaking and his willingness to say the politically unsayable will make him a central figure in the election.

Cameron, on holiday in Portugal, tweeted, “Great news that Boris plans to stand at next year’s general election — I’ve always said I want my star players on the pitch.” My sense is that Johnson’s re-entry into parliamentary politics (he was previously MP for the safe Conservative seat of Henley) significantly increases the Conservatives’ chances for victory next year.