Tuesday's alleged town hall meeting between Barack Obama and John McCain, their penultimate meeting before the presidential election, had to be judged as much on style as substance. Excessive caution by both campaigns led to a format that failed to offer many opportunities for the candidates to challenge each other or to engage in meaningful conversations with their questioners. Both candidates were wary of making a gaffe so late in the game. They moved like two dogs who thought about fighting but weren't sure which one would prevail.

Neither candidate broke much new ground, but the surprise of the night came from McCain, who announced that as president he would orchestrate a bailout plan to buy up the mortgages of homeowners in trouble and write them down to affordable levels.

Obama, however, won big on style points. He seemed comfortable, cogent and calm, while McCain, at times, scowled and showed flashes of anger and snappishness.

Their difference in age was stark. Obama stood ramrod straight. McCain hunched and, though the town hall meeting is his forte, seemed uncomfortable. His answers, particularly his repeated referral to the audience as "my friends," had all the freshness of a "take my wife" joke.

The mortgage buy-up, the sole new point of substance that evening, isn't really that new. It has passed Congress in a less expansive form, and it was recommended by Obama earlier this fall. McCain put no meat on the bones of his hasty proposal, so what he meant at the time wasn't clear. He wasn't, it turned out, suggesting that taxpayers spend $300 billion in addition to the $850 billion allotted for the bailout plus the provisions added to make its passage possible. He wants to divert $300 billion from that effort to fund his plan.

Depending on how it's done, buying up mortgages to keep people in their homes makes sense. It keeps families housed and the asset protected. Conversely, allowing tens or hundreds of thousands of homes to go into foreclosure would add to the forest of "For Sale" signs on America's lawns, further depressing housing values and the value of the investment vehicles based on them.

But McCain's plan, as explained yesterday by his chief economic adviser, Douglas Holz-Eakin, has a fatal flaw. It calls for taxpayers to pay lenders the full value of the mortgage as written and then to write debtors new mortgages for their homes' current value. Taxpayers would, for example, pay $500,000 to a lender and then sell the home back to people who, in many cases, bought more house than they could afford, for $300,000. The more expensive the home and the bigger the homeowner's gamble, the more he or she would be rewarded by government. Any such bailout plan should cap the amount of potential aid and, to the extent possible, help legitimate homeowners, not real estate speculators.

McCain's plan would bail out homeowners who can't meet their payments and foundering lenders, who bet that home values would continue inflating forever. But it would saddle taxpayers, many of whom struggle to pay their own bills, with an enormous burden. Paying off individual mortgages might be justified, but not unless the homeowners who gambled and the lenders who made enormous profits on them also lose.