Washington ? With the nomination of Samuel Alito, the nation’s long-term needs and the president’s immediate needs converge.

Our nation properly takes its political bearings, always, from the Constitution, properly construed on the basis of deep immersion in the intellectual ferment of the Founding Era that produced it. That is why our democracy inescapably functions under some degree of judicial supervision. The nation has long needed a serious debate about the proper nature of that supervision. And the president needed both a chance to demonstrate his seriousness and an occasion to challenge his Democratic critics to demonstrate theirs in a momentous battle on terrain of his choosing. The Alito nomination begins that debate.

When Churchill’s wife said it was perhaps a blessing in disguise that British voters turned him out of office even before the war in the Pacific ended, he growled that, if so, it was very well disguised. President Bush must realize that the failure of the Harriet Miers nomination was such a blessing.

He quickly cauterized that self-inflicted wound and acted on this political axiom: If you don’t like the news, make some of your own. Presidents are uniquely able to do this, and Bush, because of his statesmanlike termination of the Miers nomination, was poised to reorient the national conversation. And because of the glittering credentials that earned Alito unanimous Senate confirmation to the 3rd U.S. Circuit Court of Appeals, those Democrats who are determined to oppose him are unhappily required to make one of two intellectually disreputable arguments.

One is so politically as well as intellectually untenable that they will try not to make it explicitly. It is that judicial conservatism may once have been a legitimate persuasion, but now is a disqualification for service on the Supreme Court.

To which there is a refuting question: Since when? Since 1986, when 98 senators – including 47 Democrats – voted to confirm Antonin Scalia 98-0? Since last December, when Harry Reid, leader of Senate Democrats, said that Scalia would be a fine nominee for chief justice?

Reid doubtless would respond that Scalia would have been acceptable only because he was replacing someone comparably conservative – William Rehnquist. Which brings us to the second disreputable argument Democrats will be reduced to making: Because Alito is more of a judicial conservative than was Sandra Day O’Connor, he is unacceptable because it is unacceptable to change the court’s intellectual balance. This argument is triply flawed.

First, nowhere is that rule written. Second, the history of presidential practice – Democrats should especially study FDR’s sweeping alteration of the court’s composition – refutes the rule. Third, when in 1993 the Senate voted to confirm the very liberal Ruth Bader Ginsburg, former counsel to the American Civil Liberties Union, to the seat being vacated by the retirement of the conservative Byron White, 96 senators voted for her, including 25 Democrats still serving in the Senate. Including Reid. Including Pat Leahy, Ted Kennedy, Joe Biden, Dianne Feinstein, Herbert Kohl and Russ Feingold, all members of today’s Judiciary Committee.

Reid urged the president to nominate Miers, whose withdrawal Reid says he laments. Now Reid deplores the Alito nomination because it was, Reid says, done without Democratic “consultation.” But it was during such consultation that, Reid says, he warned the president not to nominate Alito. So Reid’s logic is that nothing counts as consultation unless it results in conformity to Democratic dictates.

When Reid endorsed Scalia for chief justice, he said: “I disagree with many of the results that he arrives at, but his reason for arriving at those results are (sic) very hard to dispute.” There you have, starkly and ingenuously confessed, the judicial philosophy – if it can be dignified as such – of Reid and like-minded Democrats: Regardless of constitutional reasoning that can be annoyingly hard to refute, we care only about results. How many thoughtful Democrats will wish to take their stand where Reid has planted that flag?

This is the debate the country has needed for several generations: Should the Constitution be treated as so plastic, so changeable that it enables justices to reach whatever social outcomes – “results” – they, like the result-oriented senators who confirm them, consider desirable? If so, in what sense does the Constitution still constitute the nation?

This is a debate the president, who needs a victory, should relish. Will it, as Democrats mournfully say, “divide” the country? Yes. Debates about serious subjects do that. The real reason those Democrats are mournful is that they correctly suspect they are on the losing side of the divide.

– George Will is a columnist for Washington Post Writers Group.