The presidential debates have been the ultimate reality TV. They freed a canned campaign from the spinmeisters and attack-ad manipulators and put it in the nation's living rooms, where people could make up their own minds.

After the public has spent three evenings with John Kerry and George Bush, it will be harder to tell people what to think about these men. We've seen them answering questions under pressure; we've watched them grimace and frown and gloat and, very occasionally, laugh; we've heard them talk about their families and their religious beliefs. We now know them in the strangely intimate way that television allows -- so that we can mimic their smallest gestures and intonations.

Sure, the candidates were coached and rehearsed: Kerry seemed to have a plan for everything, and Bush couldn't stop telling us that it was a hard job and that he was prepared to lead. But in the end, it was delightfully unscripted -- a political version of "Survivor," or maybe, "I'd Do Anything."

What Kerry won in these debates was the ability to define himself in his own terms. A month ago, Bush supporters could trash Kerry almost at will. They could charge that he was a coward who had deliberately wounded himself in combat to get a medal, and the media would weigh the pros and cons as if it were a serious campaign issue. That's much harder now that we've seen Kerry for ourselves.

What Bush lost was the ability to control perceptions. He could repeat his lines about Kerry's being a flip-flopper and a dangerous liberal, but people watching the debate could match these charges against their own sense of the man. Bush could accuse the Democrat of ransoming America to a French veto through some kind of "global test," but there was Kerry to offer an instant rebuttal. The tools of modern politics have been honed, to a frightening extent, so that they can shape perceptions. But the debates neutralized that manipulative power, at least for 270 minutes.

Until the debates, the Kerry campaign was dead in the water -- a Swift boat run aground. The first encounter was powerful partly because Kerry seemed such an underdog; when his well-drilled answers made Bush scowl in frustration, the whole chemistry of the race seemed to change. Through the next two debates, Kerry never lost that quiz-kid sharpness. He seemed to have an answer for everything -- an Iraq plan, a health plan, a jobs plan. Bush responded differently each time to the relentless plan-maker: He seemed flummoxed in the first debate, furious in the second and bemused in the third. As has been widely noted, it was Kerry who had the gravitas people often describe as "presidential."

Television will never make Kerry likable. And it will never make Bush unlikable. That's the only solace the president's men can take from this three-installment series. Even when he's at his looniest (as when he said, "Need some wood?" after a Kerry gibe about his ownership of shares in a timber company), Bush seems like the ultimate regular guy. How a preppie from Andover, Yale and Harvard could pull this off is still a mystery, but it is Bush's defining gift as a politician. He can make a virtue even of his inarticulateness.

Bush was truly riveting Wednesday night when he talked about prayer. You had the sense that you were seeing into his soul -- into the religious faith that has made him such a resolute leader. There is no doubt any longer that this is a man who sees his presidency as an instrument of God's will. Kerry, too, was moving in explaining his faith -- a belief in a social gospel of "works" that, while far less personal than Bush's, is still powerful.

These debates made Kerry a serious candidate. Whether they will make him a winner depends on how people sift what they've seen and heard -- and on each side's ability to get its supporters to the polls. The manipulators will now try to spin what we've watched on television, but it will be a harder sell. We know so much more about these men.

No wonder incumbent presidents don't like debates. They have everything to lose and very little to gain. By agreeing to debate his rival, a president moves from a unique position of power, radiating the glow of the presidency, to a level field. He gives up his best weapon and allows his opponent to overcome his greatest liability. And that's before they begin talking. If Bush should lose in November, I wonder if an incumbent will ever again submit to the same trial by television in three 90-minute slices of reality.