All weekend Republicans will be pushing the line that former Rep. Mark Foley’s dirty emails are an isolated episode that shouldn’t doom the entire Grand Old Party.

Former House Speaker Newt Gingrich has said that American society has a double standard when it comes to inappropriate or unlawful sexual behavior by lawmakers. It is wrong that Democrats get away with things while Republicans don’t.

It is Newt who is wrong this time. Voters may indeed leave the Republican Party in enough numbers to count. And they won’t do it in outrage over Mr. Foley’s alcohol-induced instant messages or unbecoming behavior by other lawmakers. No, voters will leave out of sheer embarrassment.

Consider the history of social conservatism in modern politics. From time to time, Democrats have tried to present themselves as the party of moral probity, marital fidelity, and pleated school uniforms. But let’s face it. Few believed them.

Republicans, however, have managed over the past few decades to convince a number of voters that they should and could use national office to write laws that make Americans live a more upright life. This aggressive social conservatism made the rest of the party’s traditional constituents — free marketers and moderates, for example — uncomfortable.

These latter voters had little choice. If they wanted to elect lawmakers who would fight for low capital-gains tax rates or tort reform, they had to buy tables at breakfasts with Christian conservative Ralph Reed. They had to team up with those who want a Washington-led ban on gay marriage through a constitutional amendment.

Accepting a leadership of heated moralizers was always embarrassing to these more old-fashioned Republicans. Now it’s beyond embarrassing.

There is, to start with, the extent of the Foley problem.

The Florida lawmaker played a central role in writing federal policy on the abuse of minors. He worked with the family of Adam Walsh, the 6-year-old child who disappeared 25 years ago from a Florida shopping mall, to pass a law creating a national registry of sex offenders that President Bush signed with fanfare this summer.

The recent discovery about Mr. Foley was that he sent e-mails to a minor about sex. What does this say about the seriousness of government when it comes to enforcing the Adam Walsh law?

This week, Mr. Walsh told the press he was “appalled” at the Foley news. So are the rest of us, Republicans included.

As if Mr. Foley weren’t enough, the Republicans this season also have Don Sherwood on their hands. Mr. Sherwood, a congressman from Pennsylvania, was one of the point men in the opposition to late-term abortion.

Now he is wandering the state trying to convince voters that the disclosure of a lengthy extramarital affair shouldn’t affect their decision about re-electing him. His television advertising includes a statement from Mr. Sherwood in which he says he is “truly sorry” about cheating on his wife. The spot is called “Count on Me.”

At some point — now — the average Republican will begin to say: Come on, ladies and gentlemen. Is social conservatism as national policy really worth it if so few can live up to it?

Too often the loudest advocates for protecting children or marital fidelity are those who abuse those very principles. What seems worse, many of the sinners don’t seem to believe they can stop themselves.This week another Republican congressman, Ray LaHood of Illinois, called for temporarily shutting down the congressional page program. This suggests that Congress believes that the only way it can stop members from jumping minors is to deprive them of their presence.

Even the old notion that giving in to social conservatives means winning on economics is questionable. Sometimes living up to official social conservatism gets in the way of promulgating necessary policy.

The Foley affair may claim other victims. House Speaker Denny Hastert is going to lose credibility in his home state of Illinois on serious topics such as Iraq. His Democratic challenger, Tammy Duckworth, lost both legs when her National Guard helicopter was shot down in Iraq. Next to Tammy, apologetic Denny will look worse than weak. He will look silly.

This week, when he wasn’t doing damage control, Mr. Gingrich was busy publishing a studious op-ed in Investors Business Daily on health-care reform. Mr. Gingrich is the sort of leader the House needs right now. His reforms would have a much greater likelihood of passage if he were still in office.The reason he isn’t is that he spent too much time on a social conservative’s cause: pressing the impeachment of President Clinton after his relationship with Monica Lewinsky. (Later, court testimony showed that Mr. Gingrich himself was having an affair while speaker.)

Such damage isn’t necessary. Republicans, on balance, remain a more compelling party. They have been consistent on the war in Iraq. Their economic policy ensured that the recent recession was mild, not devastating. Voters may yet sustain the GOP come November. But only if they can stand the embarrassment.

Miss Shlaes is a columnist for Bloomberg News.