Many political campaigns run against the wrong candidate. The opportunity to pick on a vulnerable target is so tempting that they are lured into attacking someone who isn’t running. In 1992, the Republicans unleashed their convention barrage at Hillary and left Bill unscathed. In 1996, Dole still ran against Clinton the liberal and ignored the changes in his political positioning. Campaigns go after the flaming red cape, so glittering a target, and leave the matador alone.

That’s what the Democratic convention has been doing in Denver. They are so anxious to run against Bush, their animosity is so pent up, that they persist in running against a man who is not seeking a third term. In speech after speech, the Democrats knock the Bush record and then add, lamely, that McCain is the same as Bush. Or they call the McCain candidacy Bush’s third term. It was no accident — or Freudian slip — when Joe Biden spoke of John Bush instead of George in his litany of attacks.

This pattern of shooting at the decoy, not the duck, gives McCain a bold strategic opportunity. He can nullify the impact of the entire Democratic convention simply by distancing himself from Bush.

The truth is, of course, that McCain is the most unlike Bush of any of the Republican senator. (When Obama’s people claim that Bush and McCain voted the same 94 percent of the time, they forget that most of the votes in the Senate are unanimous.) The fact that McCain backs commending a basketball team on its victory doesn’t mean that he is in lockstep ideologically with the president.

The issues on which McCain and Bush differ are legion:

* McCain fought for campaign finance reform — McCain-Feingold — that Bush resisted and ultimately signed because he had no choice.

* McCain led the battle to restrict interrogation techniques of terror suspects and to ban torture.

* McCain went with Joe Lieberman on a tough measure to curb climate change, something Bush denies is going on.

* McCain opposed the Bush tax cuts when they passed.

* McCain urged the Iraq surge, a posture Bush rejected for years before conceding its wisdom.

* McCain favors FDA regulation of tobacco and sponsored legislation to that effect, a position all but a handful of Republican senators oppose.

* McCain’s energy bill, also with Lieberman, is a virtual blueprint for energy independence and development of alternate sources.

* After the Enron scandal, McCain introduced sweeping reforms in corporate governance and legislation to guarantee pensions and prohibit golden parachutes for executives. Bush opposed McCain’s changes and the watered-down Sarbanes-Oxley bill eventuated.

* McCain has been harshly critical of congressional overspending, particularly of budgetary earmarks, a position Bush only lately adopted (after the Democrats took over Congress).

Remember that McCain ran against Bush in 2000.

McCain’s Republican advisers need to realize that they won the primary and that they do not need to cotton to the delegates at their convention or to appease the Bush White House. The more they respond to Obama’s and Biden’s attacks on Bush by saying, “It ain’t me, babe,” the more he will moot the entire purpose of the Democratic convention.

It is a rare opportunity to nullify the entire Democratic line of attack, and McCain should seize on it.