Conservatives differ with Mr. Giuliani on social issues. He’s committed to balancing the budget, stopping pork-barrel spending, not raising taxes, fixing entitlements, growing the economy, enhancing national security, building our military, and fighting terrorism. Aside from social issues, that’s the entire conservative agenda.

And the social issues will be decided by the Supreme Court.

Mr. Giuliani — who was part of the Reagan Justice Department — repeatedly says what kind of justices he would appoint. He names Antonin Scalia and Sam Alito as examples of whom he would nominate. They’re exactly the sort of justices conservatives have fought for years to get on the Court.

And there are safeguards in place. Supreme Court confirmations are not what they used to be. Whole organizations focus on it. Everyone knows who’s on the short list. There’s no chance of another Souter, where a supposed conservative turns out to be a liberal. No one gets the benefit of the doubt. Remember Harriet Miers.

If social conservatives disagree with Mr. Giuliani they should work to beat him in the primaries. Why the allure of the quixotic “third party” rather than a real, principled primary fight? If the issues are life, marriage, and Second Amendment freedoms, and the objective is to win, a good bet seems to be Mike Huckabee. He is right on these issues. And, he has been highlighted by pundits on all sides as the one to watch for a breakthrough.

Several of the current Republican candidates could make strong and effective presidents. My point is that they’re all equal on what social conservatives should care about most — the direction of the Court.

Rather than hand the White House, and therefore the Supreme Court, to Hillary Clinton without a fight, social conservatives and evangelicals should make a hard, principled stand in Iowa, New Hampshire, Michigan, South Carolina, and Florida on behalf of their preferred candidate. If they are not successful, and Mr. Giuliani is the nominee, they should work hard for his victory while constantly reminding him of his intentions regarding judicial appointments.

And, Mr. Giuliani, if successful, has a responsibility to reach out and talk with social conservative leaders. He cannot go around the movement’s leadership. Millions rely on them to benchmark candidates. Ignoring them will cost Mr. Giuliani millions of votes and the White House.

If he is willing to dialogue, then conservative leaders need to engage him. Earl Warren, David Souter and others have surprised the Republican presidents who nominated them. With Mrs. Clinton, there will be no surprises.