LONDON — I am not a betting man, but if I were, I would hazard $100 that Britain will have a new prime minister before America has a new president. By the time that either Senator McCain or Senator Obama is settling into the White House next January, the chances are that the new resident at Number 10 Downing Street will already have booked his or her flight to Washington D.C.

Hold on a minute, I hear you saying — hasn’t there only just been a change of prime minister? That Scottish guy, the one who isn’t Tony Blair — Gordon Brown — what’s happened to him?

Well, we Brits don’t like to mention that name these days. Seems he can’t do anything right. He has been the most unpopular prime minister for so many months now that it’s no longer news. A couple of weeks ago Mr. Brown’s Labor Party lost a special election in Glasgow, which is a bit like a Bush losing in Houston or a Clinton in Little Rock.

The economy has been headed south for some time, of course, but the effects are being felt everywhere now and there is no way for Mr. Brown, who ran the Treasury for 10 years under Mr. Blair, to avoid the blame for everything that is going wrong.

The summer “silly season” is supposed to give us all a break from party politics, or at least a ceasefire; but nothing could be sillier than the notion that politicians ever take a break from politics. So it has proved this year.

Mr. Brown is taking his annual vacation in Britain this year to save carbon emissions — Cape Cod is his destination of choice, but fear of being seen sunning himself abroad, combined with his native Puritanism, kept him at home. No sooner was the prime minister gone, than Foreign Secretary David Miliband, the young pretender from the House of Blair, raised his standard.

Writing in the Guardian, the Left’s house magazine, Mr. Miliband not only demanded a new direction for the Labor Party but — this was the key point — did not mention Mr. Brown once. He made Mr. McCain’s endorsements of President Bush seem positively cordial.

You need to know two things about Mr. Miliband. First, there are two of him. That is to say, there are two Mr. Milibands: Brother David and Brother Ed. Both are in the Cabinet, both have enjoyed “meteoric” careers, though nobody is sure what they are supposed to have done. They are not twins, like the former prime minister and current president of Poland, but most people find it difficult to tell them apart.

The second thing to know is that the Miliband brothers are the sons of a Left-wing professor, Ralph Miliband, who was quite possibly the last man in Britain who believed to his dying day that Karl Marx had been right all along. The brothers have let it be known that once they were both working for Mr. Blair they had arguments over the kitchen table with their dad. He was, perhaps, too polite to accuse them of “selling out,” but he never got over the collapse of socialism and died in 1994.

If you want a portrait of Miliband Senior, look at Tom Stoppard’s character Max in “Rock n’ Roll,” his play about Prague in 1968. Max is a Cambridge academic who dismisses his Czech dissident student with the words: “I’d be a Communist with Russian tanks parked in Trinity quad.”

There are plenty of people left in England who still treat the dissidents of the Cold War with contempt. Andrew O’Hagan, for instance — a minor novelist who is not fit to be mentioned in the same sentence as Solzhenitsyn — couldn’t wait to dance on the great man’s grave this week. Writing in the Daily Telegraph of all papers, Mr. O’Hagan sneered that “Solzhenitsyn’s writing fails to outlive its subject” — missing the point that it was his books and others like them that mortally wounded the evil empire. But the likes of Mr. O’Hagan no longer dare to defend the Soviet Union. Ralph Miliband did.

So David Miliband, the man who wants to replace Mr. Brown in Downing Street, grew up in a milieu where names like Solzhenitsyn, Sakharov, Sharansky, or Havel were uttered, if at all, only when accompanied by a curse.

This tells us very little about what Mr. Miliband would be like as prime minister, but we may be sure that the rigors of a Marxist education have left their mark on a man who is seen as the most loyal Blairite in the Cabinet, but who completely lacks Mr. Blair’s most important motivation: his Christian faith.

At this point, it is impossible to predict whether the contest between Messrs. Brown and Miliband will come to a head sooner or later. It is also possible that, if Mr. Brown shows any sign of relinquishing office, one or more other contenders will emerge.

For the moment, both the Brown and the Miliband camps are firing ranging shots at one another from the relative safety of vacation. Mr. Blair himself was dragged into this phoney war last weekend. An old memorandum surfaced that, it was claimed, reflected his dismay at the “hubris and vacuity” of Mr. Brown’s government, which had junked the Blair legacy without having anything to put in its place.

Mr. Brown can’t soldier on for much longer under this kind of pressure. His fate may well be decided next month, at the Labor’s annual party conference in Manchester. If he falters, there will be a Labor leadership contest and possibly a general election too — long before a new American president is inaugurated in January.

Mr. Johnson is editor of Standpoint.