WASHINGTON — As the Afghanistan War intensifies — Marja, soon Kandahar, and the steady arrival of 30,000 new American troops — it has come to be seen as Obama's war.

Not so. It's become America's war. When the former opposition party — habitually anti-war for the last four decades — adopts, reaffirms and escalates a war begun by the habitually hawkish other party, partisanship falls away, and the war becomes nationalized.

And legitimized. Do you think if John McCain, let alone George W. Bush, were president, we would not see growing demonstrations protesting our continued presence in Iraq and the escalation of Afghanistan? That we wouldn't see a serious push in Congress to cut off funds?

Why not? Because Barack Obama is now commander in chief. The lack of opposition is not a matter of hypocrisy. It is a natural result of the rotation of power. When a party is in opposition, it opposes. That's its job. But when it comes to power, it must govern. Easy rhetoric is over, the press of reality becomes irresistible. By necessity, it adopts some of the policies it had once denounced. And a new national consensus is born.

In this case, the anti-war party has followed the Bush endgame to a T in Iraq and has doubled down in Afghanistan. And there is no general restiveness (at least over this).

The rotation of power is the finest political instrument ever invented for the consolidation of what were once radical and deeply divisive policies. The classic example is the New Deal. Republicans railed against it for 20 years. Then Dwight Eisenhower came to power, wisely left it intact, and no serious leader since has called for its repeal.

Similarly, Bill Clinton consolidated Reaganism, just as Tony Blair consolidated Thatcherism. In both cases, center-left moderates brought their party to accept the major premises of the highly successful conservative reforms that preceded them.

A similar consolidation has happened with many of the Bush anti-terror policies. In opposition, the Democrats decried warrantless wiretaps, rendition, and detention without trial. But now that they are charged with protecting us from the bad guys, they've come to view these as indispensable national security measures.

Some other Bush policies have been challenged by the new administration with its proposed civilian trial for Khalid Sheik Mohammed, Miranda rights for the Christmas Day bomber and pledging to close Guantanamo as of two months ago. But even here, the governing administration is bending to reality. And if (in my view, when) Obama does send KSM back to a military tribunal, that institution will become fully legitimized, understood to be the result of practical empirical considerations rather than of a mere George Bush whim.

This is not to say that the rotation of power is all about consolidation. It's also about challenge. Obama may have accepted (if grudgingly) much of the post-9/11 anti-terror policy — even the wars — but he's raised a fundamental challenge to three decades of Reaganite domestic orthodoxy.

This is also to the good. The Reaganite dispensation of low taxes, less regulation and reliance on markets should be challenged lest it become merely rote and dogmatic. Obama has offered a bracingly thorough attack on that dispensation with his unapologetic embrace of a social democratic agenda whose essence — more centralized government exercising its power through radical health care, energy and education reform — is the overthrow of Reaganism.

I've made clear what side I take in this debate. I'm encouraged that Obama has been defeated on cap-and-trade and is on the defensive on his health care reform. I'm somewhat more sympathetic but still uneasy about his vision of turning college education into a federal entitlement. But for all the hand-wringing about broken government, partisanship, divisiveness and gridlock, it's hard to recall a more informed, more detailed, more serious, more prolonged national debate than on health care reform.

True, the rotation of power inevitably results in stops and starts and policy zigzags. Yet for all its inefficiency, it in the end creates a near miraculous social stability by setting down layers of legitimacy every time the opposition adopts some of its predecessor's reforms — while at the same time allowing challenges to fundamental assumptions before they become fossilized.

So, in the middle of the current food fight, as the plates and the tarts and the sharper cutlery fly, step back for a moment. Hail the untidiness. Hail democracy. Hail the rotation of power. Yes, even when Democrats gain office.