The coming weeks will answer one very important question about John McCain: does he want to be the Republican Party’s presidential nominee or does he want to be president?

Senator McCain is lucky that the race is still close, the most recent Rasmussen poll showed him being tied with Barack Obama. So far, Mr. McCain’s campaign has been abysmal: wooden set-piece speeches, poor visuals, and off-message surrogates. A former Texas senator and the candidate’s purported top economic adviser, Phil Gramm, uttered the most damaging comment, when he referred to the economically embattled American people as “whiners” — an act that reinforced the perception that Mr. McCain is out of touch on fiscal matters.

The answer to many of Mr. McCain’s problems is looming in plain, uncomfortable sight: He needs a running mate who can immediately infuse the campaign with energy, a fluid surrogate who can hammer away at Mr. Obama, stay focused, not lose his cool, and, most of all, an economic expert, who can negate, if not reverse, the Democrat’s perceived advantage in the areas of jobs and growth. The man who possesses those qualities is the same person who got under Mr. McCain’s skin during the primary fight — Mitt Romney.

To suggest that Messrs. McCain and Romney present an unlikely team is obvious to any observer of Republican politics. Mr. McCain speaks his mind and is even caustic in public; the former Massachusetts governor is smooth to the point of being slick. Mr. McCain, in both actions and appearance, is gritty, gutsy, and courageous; Mr. Romney, with his telegenic hair and shirt and tie ensembles, evokes a 1950s anchorman-like android quality.

Mr. McCain spent much time abroad in the 1960s as a prisoner of war in a North Vietnamese prison camp; Mr. Romney attempted to proselytize on behalf of his Mormon faith in the French countryside during the same period. Mr. McCain is a self-described computer “illiterate” who relies on his wife to help him online; Mr. Romney’s preferred method of presentation is computerized power point. These disparate qualities, when fused together in the odd alchemy of ticket politics, add up to a notable combination.

Half a year ago, Mr. McCain emerged at the top of the Republican field, and deservedly so. Voters selected the best well-known, tested, and heroic candidate. Mr. Romney came closest to Mr. McCain, but his skills as a former business executive, corporate turn-around artist, and governor seemed less suited to running an America imperiled by foreign foes than Mr. McCain.

Now, Mr. Romney’s attributes are much more valuable. The day of the New Hampshire primary, the Dow Jones Industrial Average stood at 12,827. As of Monday morning, it was 11,100. In November 2007 only 15% of those polled by the Pew Research Center cited the economy as the issue they most wanted candidates to discuss; that number now stands at 44%, making the economy the most important issue.

By Election Day in November, the economy likely will be an even more urgent issue. Mr. McCain will need a strong partner to tackle that issue. And all eyes are on Mr. Romney to help with that task.

Moreover, Mr. Romney brings succor to Mr. McCain geographically as well. The son of a former governor of Michigan, Mr. Romney could aid Mr. McCain in the industrial state ravaged of jobs. Yesterday, Mr. Romney appeared at the opening of Mr. McCain’s Farmington Hills office, just west of Detroit. Having gained a reputation as the savior of the Salt Lake City Olympics, Mr. Romney is well known throughout the mountain states, for which Mr. Obama is making a play, and where Mr. Romney’s Mormon faith could be a vital asset.

The typical counterargument against Mr. Romney focuses on the ill will between him and Mr. McCain. This was very visible at the debate at the Reagan Presidential Library in January. In politics, the general rule is that it’s a bad idea to place a rival in a subordinate position. In this case, however, given Mr. McCain’s age, Mr. Romney’s own ambition could allay those apprehensions. Boston Herald columnist Howie Carr, writing in a style that attempted to mimic Mr. Romney’s own internal voice, stated that “being on the ticket with him would make you the early front-runner for the Republican nomination in 2012.”

Yet when contrasted to the so-called allies of Mr. McCain, such as Phil Gramm, a Texas senator who is Mr. McCain’s friend and erstwhile economic adviser. Mr. Romney already has helped his former foe. Since Mr. Romney dropped out of the presidential race and endorsed Mr. McCain, he has been the consummate loyal soldier, holding fundraisers for Mr. McCain and tirelessly appearing on television on the candidate’s behalf.

The reality is that with a little more than three months left before Election Day, no other Republican brings to the ticket what Mr. Romney offers. If Mr. McCain is serious about winning, Mitt Romney is his best running mate.

Mr. Gitell (gitell.com) is a contributing editor of The New York Sun.