There’s something missing from the Barack Obama campaign this weekend: virtually all mention of his primary opponent, Senator Hillary Rodham Clinton. In speeches and in brief press conferences, Senator Obama has been pounding away on the presumptive Republican nominee, John McCain, often using identical rhetoric that was served up against Clinton just days ago. All day Friday and again on Saturday, Mr. Obama has been unrelenting in his attacks on Mr. McCain’s so-called Gas Tax Holiday plan, which Mr. Obama ridicules as saving motorists “a quarter and a nickel a day” through the summer. It’s same attack he launched against...