Mitt Romney’s decision to quit the presidential race is a win for both him and the Republican party. It’s a win for Mr. Romney because he made his exit in a statesmanlike manner at yesterday’s Conservative Political Action Conference meeting in Washington, D.C., before Senator McCain took the stage. This opened the door for Mr. McCain to get fervent applause from the conservative audience, a group he needs for the success of his candidacy.

That statesmanlike gesture positions Mr. Romney as a natural Republican frontrunner for 2012 or 2016. In his withdrawal speech yesterday at CPAC he said, “If I fight on in my campaign, all the way to the convention, I would forestall the launch of a national campaign and make it more likely that Senator Clinton or Obama would win. And in this time of war, I simply cannot let my campaign be a part of aiding a surrender to terror.”

Mr. Romney can still influence the party’s platform through his 269 delegates, just as Ronald Reagan did in 1976, when he failed to win the nomination. Mr. Romney signaled as much when he said, “Even though we face an uphill fight, I know that many in this room are fully behind my campaign. You are with me all the way to the convention. Fight on, just like Ronald Reagan did in 1976.” That also sounds like a hint that Mr. Romney contemplates challenging a sitting Democratic president in 2012.

Mr. Romney’s exit is a boon to the Republican Party because it might moderate, if not end, the partisan infighting on the Right that has become increasingly virulent. Talk-radio hosts, notably Rush Limbaugh, are telling their listeners that a vote for a Democratic candidate is preferable to one for Mr. McCain, now the presumptive nominee. If Mr. Limbaugh were to continue his unrestrained polemics against Mr. McCain, then the talk-show host would look silly.

Republicans now have the opportunity to unite nine months before election day, bind up intramural wounds, and save their funds and energy for the national race, rather than tearing each other apart, as the two contending Democrats are doing.

Mr. McCain needs to get more Republicans to like him enough to support him actively. Republicans will vote for him, but they may not go to the effort of raising funds, and, most important, getting out the vote. Turnout among Democrats in the primaries has been at record levels, reflecting enthusiasm. To win the presidency, Mr. McCain has to inspire his followers to equal ardor and effort.

This has nothing to do with Mr. McCain’s credentials as a bona fide conservative. Although Mr. Romney would have Republicans believe that he is the only conservative, Mr. McCain’s credentials are equally valid, as was apparent by his reception at CPAC. He is supported by Phil Gramm of Texas, Senator Coburn of Oklahoma, New York’s Jack Kemp, and Governor Barbour of Mississippi.

Mr. McCain has been consistently strong on defense, advocating an unpopular troop surge in Iraq before President Bush. He has always favored less nonmilitary spending, campaigning in Iowa against ethanol subsidies and voting in 2003 against Medicare expansion. Although he didn’t vote for President Bush’s tax cuts in 2001 and 2003, he has never voted for a tax increase. Last Sunday, he told both Fox News Sunday and CBS’s “Face the Nation” that he would veto any tax increase if elected president.

In Washington, some Republicans don’t like Mr. McCain because he hasn’t worked with them as a team player. Congress, like many legislatures, has a buddy system — you support me on my projects and I’ll support you on yours. Mr. McCain has never played that game and that has earned him enemies within his party, leaving bridges that need to be repaired or built.

On the other hand, Mr. McCain’s nonconformist instincts appeal to people outside the party, which will improve his chances in November. Senator Lieberman, an independent, has frequently campaigned with the Arizonian. Registered Democrats exceed Republicans, and many Democrats are uneasy about the liberal Mrs. Clinton and the radical Mr. Obama. To these centrists, Mr. McCain might be a Republican they can support.

The best of all worlds would be to attract grassroots Republicans, disaffected Democrats, and independents. That is Mr. McCain’s challenge.

And Mr. Romney’s early exit gives Mr. McCain an advantage he did not have on Super Tuesday.

Ms. Furchtgott-Roth, former chief economist at the U.S. Department of Labor, is a senior fellow at the Hudson Institute. She can be reached at dfr@hudson.org.