WASHINGTON (CNNMoney) -- Howard Gleckman is a resident fellow at the Urban Institute and editor of TaxVox, the blog of the nonpartisan research organization Tax Policy Center. The opinions expressed in this commentary are solely those of the writer.

The story goes that when Lyndon Johnson was losing his first congressional election, he put out word that his opponent was having sex with barnyard animals. An aide innocently warned Johnson that this wasn't true. "Make the SOB deny it," LBJ was said to have replied.

So goes the current debate over the Bush tax cuts.

To start, not a single important Democrat favors letting all the Bush tax cuts expire at the end of the year, as the Republicans on the House Ways and Means Committee allege. Ever since his campaign...