The unfolding controversy over class warfare in American politics took a new turn yesterday with the entry of Senator Lieberman, the Democrat from Connecticut, into the presidential campaign. To recap: Democrats in Congress have been denouncing the Bush tax cut as a gift to the rich. President Bush has been denouncing the Democrats for engaging in “class warfare.” Some Democrats have responded by accusing Mr. Bush himself of class warfare.

Into this fray yesterday plunged the senator from the Nutmeg State, whose brand-new campaign Web site proclaims boldly “a strong middle class means a strong America.” Lifting a line from presidential candidate Bill Clinton, Mr. Lieberman made reference in his announcement speech to those who “work hard and play by the rules.”

There was a time not too long ago when Democratic presidential politics was about how to help those born into poverty, those unable to find jobs. More recently Republicans, led by compassionate conservative George W. Bush, have taken up the banner. The Republicans seek to help the poor through means-tested school voucher programs for those in failing public schools. They also support allowing social services to be delivered through churches, synagogues, and other faith-based institutions that are often remarkably effective.

As a senator, Mr. Lieberman has voted for voucher programs in the Washington, D.C. public schools, and he has expressed support for some of Mr. Bush’s faith-based initiatives. Yet it is his party, the Democrats, that is blocking those initiatives. So as the Democrats blame Mr. Bush for helping the rich, he might parry by asking Senator Lieberman, champion of the middle class, why his Democratic colleagues have been blocking aid to the poor. As the Democrats court the middle class, after all, they leave themselves open to the same class warfare attacks they have been wielding against Mr. Bush.