It's no big secret that Republicans think they own the tax issue. Newly liberated by George W. Bush from any sense of fiscal responsibility or fairness, the GOP has advanced a grotesque version of tax reform using the budget surpluses piled up during the Clinton years, plus trillions of dollars in borrowing from the Social Security trust fund and the earnings of present and future generations of Americans. Its hallmarks are an assault on the progressivity of the tax code, a shift in the tax burden from unearned wealth to wages, and a shift in the cost of domestic government from the federal to state and local governments, all lubricated by the illusion of small tax cuts for middle- and lower-income Americans.

Reports abound in Washington that Bush will propose still more election-year tax cuts in the State of the Union Address. And if he's re-elected, the Big Bertha of GOP tax policy, an assault on corporate taxation, along with a consummation of Bush's plans to abolish taxes on investment income, can be expected to follow very quickly.

Tax cuts have become a defining issue in the race for the Democratic nomination. Every candidate rightly supports repeal of Bush's tax cuts for the wealthy. Unfortunately, some have gone further and called for taking tax relief from the middle class. We agree with Senators John Kerry, John Edwards, and Joe Lieberman and Gen. Wesley Clark that the answer to a Republican administration that has kept middle-class incomes from going up should not be a Democratic administration that makes middle-class taxes go up. The mission of the Democratic Party is to expand opportunity for the middle class and all who aspire to join its rank, not add to their burdens.

We're delighted that some Democrats follow in Bill Clinton's footsteps by remembering the struggles of the forgotten middle class. Sen. Joe Lieberman has proposed a sweeping tax reform plan to make the income tax system more progressive. Sen. John Edwards has proposed a tax cut plan to help middle-class families buy a home and save for college and retirement, and make sure ordinary Americans don't pay higher taxes on the work they do than billionaires pay on their investments. Sen. John Kerry has also proposed middle-class tax relief aimed at college savings and an expansion of health care coverage.

Yesterday, in his most interesting domestic policy proposal to date, Gen. Wesley Clark unveiled his own tax reform plan. The centerpiece of the Clark plan is a two-front assault on the complexity of the tax code. First, it would combine the welter of tax credits and exemptions for families with children (including the Earned Income Tax Credit) into a unified and enhanced $2250 credit for each child in a family earning less than $100,000, effectively eliminating federal income tax liability for the typical family of four with income under $50,000. And second, it would abolish the need for tax filing altogether by families without income tax liability, as documented by a simple three-line tax worksheet.

Clark's unified child tax credit would make the tax system much more progressive, in combination with a 5 percent surcharge on earned incomes over $1 million, which partially pays for its lower- to middle-class tax relief. Low-income families, which were left out of the Bush tax plan's increase in the child tax credit, would benefit enormously from the unified credit, further improving the "new bargain" of work-based welfare reform initiated by the Clinton administration.

There are plenty of legitimate questions about the Clark plan. As Sen. John Edwards' campaign pointed out, Clark's millionaires' tax surcharge would only apply to earned income, which means the truly idle rich would be exempted.

But Clark's support for tax reform, based on progressivity, simplicity, support for working families, and shared responsibility for the cost of government, moves in exactly the right direction. He joins Lieberman, Edwards, and Kerry as a Democrat willing not only to resist and reverse the Republican assault on the longstanding bipartisan principle of progressive taxation, but to increase progressivity at a time when the very wealthy owe something more back for the blessings of a free society.

We hope all Democrats take advantage of this moment to broaden and deepen that national debate on taxation beyond rearguard actions against Republicans assaults on the commonwealth. In particular, Clark's initiative should light a fire under front-running candidate Gov. Howard Dean, who continues to insist that the middle class never got a tax cut so he's not obligated to preserve it. Democrats can win the tax issue, but only if they combine a willingness to propose tax reform and middle-class tax relief with a determination to make government as responsible and efficient as possible. That's part of the unfinished but promising legacy of the Clinton administration, and it's the right thing to do as a matter of both principle and politics.