He's more powerful than House Speaker John Boehner (R-Ohio), Senate Majority Leader Mitch McConnell (R-Ky.) and the Koch brothers, yet not many people have heard of Grover Norquist or his "Taxpayer Protection Pledge."

Mr. Norquist, founder and president of the Americans for Tax Reform (ATR), is simply the single most influential Republican of the past 25 years.

Politicians may come and go, but since 1985, Mr. Norquist has been getting an increasing number of Republicans to sign his tax pledge to the point where he now has 237 members of the House and 41 in the Senate at his disposal.

When you have the majority of the House -- including House Budget Chairman Paul Ryan (R-Wisc.) and enough votes in the Senate to prevent legislation from coming up for a vote, that's real power.

When your organization's tax pledge is THE litmus test for Republicans running for office on the national level, you wield more power in your party than anyone in Congress.

Thanks to Mr. Norquist's growing influence over the past two-and-a-half decades, failure to pledge allegiance to the "no new taxes" mantra effectively dooms one's chances of getting the GOP nod for the House, Senate or White House.

To strengthen Mr. Norquist's hand, the GOP base is challenging Senators Olympia Snowe (R-Maine) and Richard Lugar (R-Ind.) from the right -- because both refused to sign the tax pledge.

According to Mr. Norquist's tax pledge, politicians who sign it "oppose any and all efforts to increase the marginal income tax rates for individuals and/or businesses," and "oppose any net reduction or elimination of deductions and credits, unless matched dollar for dollar by further reducing tax rates."

If we want to know the real story behind the $14 trillion federal debt and our annual $1.5 trillion deficits, we have to look at Mr. Norquist and his tax pledge.

If we want to know why the Republicans won the staring contest on extending the Bush tax cuts -- which are part of the "starve the beast" strategy -- the answer is Mr. Norquist and his tax pledge.

When we have successive stopgap funding bills because the GOP's only solution to the deficit is draconian cuts, blame Mr. Norquist and his tax pledge.

And when GOP leaders at both the national and state levels try to balance the budget by cutting programs that help seniors, students, the middle class and low-income families -- take a bow, Mr. Norquist.

Because of their allegiance to Mr. Norquist's tax pledge, Republicans dismiss out of hand "revenue enhancement" measures (as President Ronald Reagan called tax hikes) such as highly-popular and common-sense ideas of raising taxes on millionaires and billionaires, Wall Street bankers and the big oil companies.

That is why the GOP went on a cutting spree on the House floor when formulating their measure to fund the federal government through the end of 2012.

And that is why the debt commission's recommendation was dead on arrival.

As long as there's a House majority and at least 41 Senators who are signed onto the tax pledge, income and long-term capital gains tax rates will not return to pre-Bush levels and the estate tax (aka "the death tax") will not go back to where it was before 2002 -- because that would be raising taxes according to Mr. Norquist.

Remember, long-term capital gains -- which one pays on investment income such as stocks, bonds and real estate -- is how the Wall Street folks responsible for the Great Recession and the corporate CEOs make their millions. For three decades, they have seen their portfolios grow exponentially, while most American household incomes have stagnated.

Wall Street and corporate CEOs owe a huge debt of gratitude to Mr. Norquist.

Clinton Labor Secretary Robert Reich wrote in his March 2 piece in the Huffington Post that investment income should be treated the same as wage income. He's right, but doing so would mean raising taxes, and unless the tax-pledge crowd loses the House and drops below 41 Senators, it's not going to happen.

On the state level, guess who else has signed Mr. Norquist's tax pledge? Union-busting governors Scott Walker (R-Wisc.) and John Kasich (R-Ohio).

With his House majority, his filibustering Senators and his union-busting governors, Mr. Norquist has his hands in every big fiscal debate -- in Washington and in the states -- for more than two decades now.

And that is why Grover Norquist is the most powerful Republican in America.