A century ago this summer, Theodore Roosevelt gave his remarkable “New Nationalism” speech about the dangers of concentrated wealth and corporate power. After witnessing a decade of financial corruption and corporate malfeasance, Roosevelt called on the nation to “effectively control the mighty commercial forces which they have themselves called into being.”

Part of his vision was a “graduated inheritance tax on big fortunes, properly safeguarded against evasion and increasing rapidly in amount with the size of the estate.” Congress instituted an estate tax in 1916 that was in place until last January. For most of the last century, the estate tax was a single tax rate. A person with $5 million was taxed at the same rate as someone with $5 billion.

A century later, a group of Senate progressives have heeded Roosevelt’s call. On June 24, four US senators introduced the “Responsible Estate Tax Act,” (S.3533) which includes a graduated rate structure that taxes billionaires at rates significantly higher than it does multimillionaires. Preliminary estimates indicate the proposed tax would generate $319.2 billion over the next decade.

Led by Senator Bernard Sanders and joined by senators Sheldon Whitehouse, Tom Harkin and Sherrod Brown, the proposed estate tax reform would close loopholes, encourage conservation easements and exclude from the tax the minuscule number of small businesses that would otherwise be subject to the tax. This estate tax rate would range from 45 percent on estates under $10 million to a 65 percent “billionaire surcharge” on estates over $500 million ($1 billion for a couple).

The timing is great, because the Senate may deliberate the future of the estate tax in July.

Due to Senate inaction last fall, the estate tax expired last January 1. The absence of an estate tax for 2010 will cost an estimated $14.8 billion this year. Already, one Texas oilman, Dan Duncan, became the first billionaire in US history to die without any estate tax in place. Duncan was worth $9 billion and would have paid an estimated $4 billion in estate taxes.

Progressives in Congress are in an advantageous position to press for a good reform. If Congress takes no action, the estate tax law sunsets on January 1, 2011, and reverts to its year 2000 levels—with a wealth exemption of $1 million and a 55 percent rate.

Unfortunately, Senate Democratic leaders are like poker players with three aces in their hands but who are considering folding. They don’t view their leverage as an opportunity to press for a bold and creative reform. Instead, they are leaving the estate tax redesign to senators Blanche Lincoln and Max Baucus, politicians committed to weakening the law.

We need a mighty mobilization to pressure the Senate to take up the Responsible Estate Tax Act. Fair tax advocates are mobilizing, including Wealth for the Common Good, a network of business leaders and wealthy investors. They are backing the legislation and have compiled fact sheets and other resources.

Theodore Roosevelt had nothing against the wealthy. “We grudge no man a fortune,” he said, “which represents his own power and sagacity, when exercised with entire regard to the welfare of his fellows.”

But Roosevelt understood that concentrations of wealth undercut the common good—and threatened democratic institutions. “The really big fortune, the swollen fortune,” Roosevelt intoned in his “New Nationalism” speech, “by the mere fact of its size acquires qualities which differentiate it in kind as well as in degree from what is possessed by men of relatively small means.”

A century later, as we live through our Second Gilded Age, we must rally for a progressive estate tax as a way to raise urgently needed revenue, create real jobs and thwart plutocracy.