George Bush, it turns out, suffers from the very same disability that has plagued Walter Mondale this entire campaign year: the "If You Only Knew Him in Private" virus.

All kinds of folks around Washington and politics will freely testify what a terrific fellow Bush is in private conversation and personal encounters. But put him, as he was in what could have been called the Valium-Dexedrine tournament in Philadelphia, and Bush turns excessive.

He is too happy with his assignments and his work. And the good work he had done Thursday night in interrupting the worst Reagan political week of the last two years was undone on Friday in New Jersey. There (in an aside to longshoremen more than faintly reminiscent of Richard Nixon's eagerness to adopt what he thought to be the argot of his immediate audience) Bush used what he defended as sports vernacular to critique his debate performance.

The lousy week included the up-to-now exemplary Mrs. George Bush referring to the Democratic vice presidential nominee, Geraldine Ferraro, by a term that Mrs. Bush said she herself was too much of a lady to speak -- but it rhymed with "rich." It didn't take Dick Tracy to figure it out after Bush's longtime press secretary, Pete Teeley, called Ferraro "bitchy" in The Wall Street Journal. You have to wonder: if Mondale had selected Texas' Sen. Lloyd Bentsen to be his running mate, would the Bush entourage have employed less gender-intensive epithets?

So the week ended with Bush back on the defensive. And that is where the Reagan campaign spent most of its time as well, especially on the campaign's new big issue: age. Supporters of the president criticized those Democrats who, eager to avoid discussion of the economy, emphasized the president's hesitancy in his faltering debate performance in Louisville.

But if the supporters had believed our president to be more vigorous and more youthful than most of his contemporaries, then credit must be given to his own staff. After all, every presidential visit to California begins with those wonderful pictures of Reagan, in his non-designer work clothes, chopping wood or clearing brush from the trails on his ranch. By now, he must somewhere have a pile of chopped wood big enough to keep every California fireplace toasty until 1990. Then the president has been photographed riding his favorite horse -- tall in the saddle, of course -- on the very trails that he has made brush-free. Earlier there was the Oval Office picture of the 73-year-old president arm-wrestling into submission some lumberjack with biceps slightly larger than an inflated basketball. This preceded the Parade magazine cover showing the leader of the free world, stripped down to his T-shirt, pumping iron.

These photos, all conceived and produced by Reagan's chief aides had only one purpose: to convince the American electorate that Ronald Reagan had found somewhere outside Santa Barbara what Ponce de Leon had spent all that time in Florida looking for. The "age" issue was introduced into the campaign by Reagan's most loyal and prominent lieutenants.

Sen. Paul Laxalt blamed the president's debate performance on "brutal" preparation sessions that somehow burdened Reagan with too many facts. But more important than the Laxalt post-mortem was the Laxalt touting of next Sunday's debate in Kansas City. The president's best friend in the Senate upped the stakes and raised the ante on the second debate: another faltering Reagan performance would change the entire last two weeks of the 1984 campaign and, quite possibly, the outcome.

Last week began with aides taking credit for Mondale's performance and ended with aides being blamed for Reagan's. But voters are smarter than all that; somehow, they know that any presidential candidate picks his own aides and his own running mate. And that he ought to be held responsible for both.