Democrats won Congress this week on a platform of fiscal conservatism. Voters believed Republicans had lost their fiscal compass and had become the party of big, reckless government. Yes, Iraq was also a big issue, but a key component of the victory was the Democrats’ ability to neutralize the Republican advantage on taxes and spending by adopting key fiscally conservative positions. The first big test of whether Democrats are serious about being a party of fiscal discipline will be on earmark reform.

Far from a repudiation of free-market, limited government principles, this election was a vindication of them. Democratic leader Nancy Pelosi and Rahm Emanuel, the chairman of the Democratic Congressional Campaign Committee, included fiscal responsibility planks in their winning “New Directions” platform, including a promise to restore discipline to the budget process and eliminate the budget deficit.

Even on taxes, Democrats largely won on a pro-growth message. A post-election analysis of 60 key House races conducted by Americans for Tax Reform found that only two winning Democrats called for higher taxes. At least nine Democrats who called for tax cuts won.

If Democrats are serious about fiscal discipline and economic growth, they will include the strong earmark reform package they campaigned on in their rules when they organize the House.

Strong earmark reform would squarely address two of the problems that voters trust Democrats to correct: wasteful spending and corruption. Earmarks are wasteful spending almost by definition, since an earmark is a project specifically funded by an act of Congress outside of the usual processes that rely on competitive bidding and the judgment of professional civil servants. Because they short-circuit the usual safeguards for spending taxpayer dollars, earmarks are a preferred vehicle of corrupt lawmakers, and are frequently seen as a way of rewarding political contributors and cronies.

In September, 147 Democrats, including Mrs. Pelosi and Mr. Emanuel, as well as likely majority leader candidates Steny Hoyer of Maryland and Jack Murtha of Pennsylvania, voted against the House Republican earmark reform plan. Why? The Republican plan failed to go far enough, in their view, since it only required the identification of which member sponsored each earmark.

At the time, Mr. Emanuel said, “The American people deserve to know more than who sponsored special interest legislation. They deserve earmark reform that puts an end to special interest earmarking, and provides solutions to prevent the practice of earmark abuse.”

The Democratic earmark reform plan, introduced by Mr. Emanuel and Chris Van Hollen of Maryland, is impressive. It would prohibit any member of Congress, his or her spouse, or immediate family member from benefiting from an earmark. It would ban the awarding of earmarks to any entity that employs or is represented by a former employee of the earmark’s sponsor, or is represented by a lobbying firm that employs any close relative of the earmark’s sponsor. It would ban tax measures to benefit one individual, corporation, or entity. And it would ban adding earmarks to conference reports that did not appear in either house’s original language.

This proposal indeed goes substantially further than the Republican reform-plan that required disclosure of earmarks but did not prohibit them.

The Emanuel-Van Hollen package would restore integrity to the budget process and end one of Washington’s worst excesses. Earmarks cost taxpayers millions of dollars, but the culture of spending they create costs taxpayers billions. Pork-barrel projects are used to curry favor for massive bloated spending bills, including the recent scandalous highway bill with its famous bridge to nowhere.

The $286.4 billion highway bill was likely the turning point that convinced fiscal conservatives to give the Democrats a turn at running Congress. According to a recent Heritage Foundation study, the 1982 highway bill contained just 10 earmarks. When the 1987 highway bill contained 152 earmarks, President Reagan vetoed it. Last year’s highway bill contained at least 6,371 earmarks and was a model of how earmarks drive overall federal spending. The bill’s managers used millions of dollars of earmarks to buy support for billions of dollars in higher federal spending.

After 12 years in power, Republicans had become the party of big government, running up record annual spending totals. Federal spending increased at a brisk rate of 7.4% in 2006, and stood at a record $2.65 trillion last fiscal year, more than 42% higher than it was during Bill Clinton’s last budget year in 2001. Spending on just one program, Medicare, increased by more than $40 billion last year alone.

The big-government Republicans outspent all Democratic records, dramatically expanding non-defense spending, creating a massive new entitlement program, and creating a massive new regulatory apparatus, Sarbanes-Oxley, while letting the pushes for tax reform and Social Security reform stall.

Voters trusted Democrats on ending corruption and keeping the economy growing. The Emanuel-Van Hollen earmark reform package would be a real accomplishment on both fronts and would show that Democrats are serious about fiscal responsibility.

Mr. Kerpen is a policy analyst in Washington.