Congressional Republicans—including freshly minted senators and representatives—will be confronted with one of the most important votes of the year when they regroup on Capitol Hill just two weeks after Election Day. It’s not the issue of electing a speaker or minority leader. It’s whether or not to extend the GOP’s earmark moratorium for the 112th Congress.

Regardless of whether Republicans win a majority in the House or Senate, the rules that govern their members will be debated and determined in mid-November. In addition to electing party leaders, they’ll tackle the contentious issue of earmarks, the congressional provisions often inserted in legislation to benefit a campaign donor or fund a specific pet project.

Sen. Jim DeMint (R.-S.C.) has vowed to bring up the matter for a vote on November 16 when his Senate Republican colleagues gather in Washington for an organizational meeting. The vote will pit critics of pork-barrel projects against earmarxists.

"I will force a vote in the Senate GOP conference to ban earmarks next year," DeMint told The Washington Times earlier this month. "I believe this will pass, and Republicans will be unified against the wasteful and corrupt earmark system."

A majority of Senate Republicans, including Minority Leader Mitch McConnell (R.-Ky.), are already on record supporting an earmark moratorium. DeMint forced a Senate floor vote on March 16, which he lost. But in the process he won the backing of 25 Republicans, a majority of the caucus, and even four Democrats.

When the GOP gathers on November 16, the vote will be conducted by secret ballot—a potentially troublesome detail, as senators then cannot be held accountable. Already, one of the most notable supporters of the March moratorium vote—McConnell—isn’t taking a position on an extension.

Meanwhile, momentum for a moratorium is building among the House GOP caucus. Thanks to a strong statement in support of a moratorium by Minority Whip Eric Cantor (R.-Va.), conservatives are contemplating their options.

Earmark opponents want a conference-wide vote the week of November 15, which would serve as a symbolic move by the House GOP and coincide with DeMint’s action in the Senate. If Republicans reclaim the House, Cantor has suggested expanding the moratorium to all members. But that vote wouldn’t happen until early January when the rules are finalized.

Much of the uncertainty rests with the outcome on Election Day. New members would be eligible to vote, and a strong influx of Tea Party candidates would boost both the House and Senate effort. But a conservative landslide could also serve as an excuse to delay action until the newly elected lawmakers are seated in January. Delaying action would be a mistake.

Nothing fuels the passion of fiscal conservatives more than their dislike of pork-barrel projects. For years earmarks have served as a gateway drug to higher spending. Or, as Cantor put it in his Politico op-ed last week, “Earmarks are a symptom of a disease—and that disease is Washington’s runaway spending.”

Conservatives greeted Cantor’s statement with glee. It meant the GOP’s top three House leaders are firmly against earmarks. Minority Leader John Boehner (R.-Ohio) has never requested an earmark and Republican Conference Chairman Mike Pence (R.-Ind.) strongly supports extending the moratorium.

Obstacles remain in both chambers, however. Rep. Jerry Lewis (R.-Calif.), ranking member of the powerful House Appropriations Committee, is a notorious earmark proponent. He and others are unlikely to accept an outright moratorium without a fight.

In the Senate, where the GOP’s prospects of winning control aren’t as promising, at least ten Republicans are on the record opposing the earmark moratorium. The good news is that four opponents of the moratorium are retiring or were defeated in a primary election this year.

Sen. Thad Cochran (R.-Miss.), vice chairman of the Senate Appropriations Committee, is one of the ten Republicans who voted against the earmark moratorium in March. He campaigned aggressively against DeMint’s amendment.

"I think the people of my state are entitled to be represented by an advocate for projects and programs that benefit our state," Cochran said at the time. "There are many outstanding civil servants within the executive branch, but those persons are not necessarily familiar with the interests of the people in our respective states and with the needs of those whom we represent.”

That’s a familiar argument among earmark supporters—one that Republicans have used with more frequency since President Obama was elected. However, it’s a losing argument. Earmarks corrupt even the most principled politicians.

If the GOP—in both the Senate and the House—fails to support action against earmarks this November, it will be an early indication that its members don’t understand the uprising sweeping across America.

Mr. Bluey, a contributing editor to Human Events, is director of the Center for Media & Public Policy at The Heritage Foundation.