Republicans are sending onto the field a presidential candidate who perhaps has the least to offer middle-class voters on taxes since the first George Bush in 1992. Of course, Bush lost that year to a Democrat promising only to raise taxes on “the rich” and to cut them for the middle class — exactly Obama’s position now. In his primary campaign, McCain had to endorse the extension of the Bush tax cuts he voted against in the Senate. But they have turned into a trap. Because Obama also wants to extend the middle-class aspects of the Bush cuts, McCain is...