An iron rule of politics holds that contested elections are won and lost in the middle. Roughly 40 percent of voters will vote for the Democrat and 40 percent for the Republican, leaving the outcome in the hands of the undecided 20 percent. The rule assumes the candidates hold on to their "bases." But sometimes they don't. Many pundits believe a liberal revolt in Democratic ranks cost Al Gore the state of Florida, and thus the presidency, in 2000. Today, Republicans in Congress, who spent 40 years in the minority before 1994, face their own brewing revolt among their base.

According to the latest CBS News poll, just 28 percent approve of the job Congress is doing, while 61 percent disapprove. These numbers are similar to what polltakers found in 1994, when Democrats lost the House of Representatives to the Republicans.

What should especially frighten Republican congressional leaders is that their support is as soft among the GOP rank-and-file as it is among Democrats. A mere 31 percent of Republicans approve of the job they're doing, while 59 percent disapprove. Why? Because these lawmakers haven't been true to conservative principles.

Consider spending.

The federal budget has swollen by nearly half since "compassionate conservative" George W. Bush took office. While that partly reflects necessary increases in homeland security and military spending, the lion's share shows extravagant spending on farm subsidies, education and pork, among other things.

Congress piled on with another un-conservative action: passing the largest new entitlement program since the '60s, the massive prescription-drug program tacked onto the already failing Medicare system. This one law will cost taxpayers $854 billion in just the first 10 years. Then it'll get really expensive.

With their approval ratings tanking and only eight months to go until Election Day, GOP leaders have a choice: Continue to act like devotees of Big Government, or rededicate themselves to the conservative principles that have captured the hearts -- and the votes -- of the base and the middle for more than 20 years. After all, there's a reason about twice as many people call themselves "conservative" as call themselves "liberal."

Congress could begin by applying the laws it passes to itself. Remember Sarbanes-Oxley? It was supposed to clean up American business by forcing companies to engage in open accounting practices. But no entity in this country is as secretive with its books as the federal government.

If, like every company in the nation, the government had to include known financial liabilities in its bookkeeping, estimates indicate the national debt would now be approaching $72 trillion.

Lawmakers need to be honest with us about the consequences of their spending and find ways to control entitlements such as Social Security and Medicare as well as other forms of spending. It's time for them to start eliminating useless or superfluous programs. For example, in 2003 the Treasury Department admitted it couldn't account for $24.5 billion. That money was spent, but nobody knows what it was used for. How about finding those missing billions?

At the same time, the federal government runs at least 342 different economic development programs. Duplicative programs waste time, money and talent. Congress should insist federal agencies do more for less.

Granted, these are baby steps. But that makes them imminently doable.

Polls show that the vast majority of Americans -- the conservative base as well as the conservative-leaning middle -- are in no mood to accept business as usual in Washington. We want government to be more responsive and more responsible.

That will require a return to the conservative principles -- such as the commitment to limited government -- that today's leaders rode into office. Otherwise, they may soon find themselves back in the minority.

Edwin Feulner is president of The Heritage Foundation (heritage.org), a Washington-based public policy research institute and co-author of the new book Getting America Right.