On Tuesday Barack Obama crushed Hillary Clinton in Virginia, Maryland and the District of Columbia. He did this while winning significant support from older voters, women, lower income earners and Hispanics -- groups that had sharply favored Mrs. Clinton in other states. And he did this after turning in decisive victories over the weekend in Louisiana, Nebraska, Washington state and Maine.

Mrs. Clinton was supposed to deliver the knockout blow on Super Tuesday. But instead, after being fought to a draw and now facing an Obama avalanche, she is taking a Giuliani Light approach. She is counting on winning in Ohio and Texas on March 4. The problem is that March 4 is nearly three weeks away, or about the same length of time between when Republicans voted in New Hampshire and when they voted in Florida. During that span Rudy Giuliani went from one of his party's frontrunners to one of its also rans.

By the time voters in Ohio and Texas head to the polls, Mr. Obama could be on a 10-state winning streak and raising funds at a clip that far outpaces Mrs. Clinton. If so, Mrs. Clinton's support could drop precipitously -- and her party's super delegates could hand their support to Mr. Obama.

So in the race for the Democratic nomination, the odds now favor the junior senator from Illinois. And if he wins, the presumptive Republican nominee, John McCain, will have his work cut out for him. Those who believe Mr. Obama will be an easy target because he is liberal and inexperienced haven't followed his campaign. If Mr. Obama is the nominee, Mr. McCain will face a politician of enormous talent and personal grace. So what can Mr. McCain do about it?

- First, he can make use of the gift of time. Having all but locked down the GOP nomination, Mr. McCain can use the next few months to reintroduce himself to the American people. It is not safe to assume that most voters have closely followed the race thus far. What many people know about Mr. McCain they like, based on his valor, honor and love of country. Now he needs to build on this by retelling his life story in a vivid, moving way.

- Second, create a compelling narrative that explains his candidacy. So far the GOP race has had a "check-the-box" quality to it. Mr. McCain needs to put issues under a broader banner. Defending American ideals against our enemies abroad, and being worthy of those ideals at home, is one banner that could have broad appeal. If Mr. McCain advocates policies that advance liberty and individual responsibility, strengthen the family, and promote prosperity, he will give his candidacy the context it needs.

- Third, turn Mr. Obama's strength into a weakness. Right now Mr. Obama is presenting himself as a figure who floats above politics. His allure is based on inspiring but vague calls for hope and unity. This airy appeal can and needs to be firmly strapped down to the policies Mr. Obama would put in place. This requires defining Mr. Obama's invocation of "change" for what it is: orthodox liberalism.

Mr. McCain, meanwhile, can be the man of substance, specific policies and reform. Presenting himself as that man, however, won't be easy. In the past, Mr. McCain has shown a lack of interest in economic and domestic issues. But it is essential now for his success. His policies need to be creative, aimed at everyday concerns, and show intellectual rigor. Remember that among the GOP's greatest electoral successes in recent decades (Ronald Reagan's election as president in 1980 and the Republican capture of Congress in 1994) were based on philosophical contrasts. Pale pastel campaigns (George H.W. Bush in 1992 and Bob Dole in 1996) are a road to defeat.

- Fourth, repair the breach with key conservatives. Mr. McCain can begin to do this by stopping advisers from making silly attacks on talk-radio hosts and instead offering specific, concrete governing commitments. Picking fights with the right people, instead of people on the right, would also help Mr. McCain. Conservatives may never love Mr. McCain. But he can strengthen ties to them by cultivating common interests.

- Fifth, broaden the national security debate beyond Iraq. Mr. McCain was right on Iraq, and he was right early. The success of the surge is a tribute to his wisdom and steadfastness on these matters. But Iraq is and will remain an unpopular war. Mr. McCain needs to speak more specifically about his policies beyond Iraq and the Middle East and articulate the philosophical core of his national security approach. And he needs to explain why he (unlike Mr. Obama) will keep America safe and on the offensive in our war against jihadism.

Mr. McCain's task will not be easy. If he is the nominee, Mr. Obama will be a formidable candidate and Democrats will likely enjoy advantages in fundraising, enthusiasm and party identification. But John McCain has overcome more difficult challenges in his life.

-- Mr. Wehner, formerly deputy assistant to President George W. Bush, is a senior fellow at the Ethics and Public Policy Center.