Federal funding for highway projects dries up at the end of July, and both parties are thinking about refilling at an oasis untapped in the Obama Presidency—pro-growth tax reform. Hallelujah if the center-right and center-left can converge on this promised land, though it may be a mirage.

Last week Senators Rob Portman (R., Ohio) and Chuck Schumer (D., N.Y.) re-energized the tax debate with a framework for reorganizing corporate taxes. The breakout idea is to improve the tax code that hurts American companies doing business...