October came early this year. In presidential politics, the penultimate month almost always brings surprises, or at least big news. In 1980, the Carter-Reagan debate that put the Gipper in the White House was not held until seven days before the Nov. 4 election. In 1992, Iran-contra independent counsel Lawrence Walsh chose the last weekend of the race to indict Reagan-era Secretary of Defense Caspar Weinberger, wounding George H.W. Bush, who was seeking re-election. In 2000, a Fox station in Maine broke the story of an old DUI of George W. Bush's, news that Bush's advisers believe hurt him in the popular vote against Al Gore. Four years ago, in 2004, a videotape of a very-much-alive Osama bin Laden stymied John Kerry's bid by sending worried voters back to the seemingly tougher Republican ticket (despite the fact that the very same Republican ticket had been unsuccessfully searching for the very same bin Laden for more than three years).

With the troubled markets and the ensuing debate over the Bush administration's proposed $700 billion bailout of the financial sector, October started in September. By suspending his campaign and threatening to postpone the foreign-policy debate in Oxford, Miss.—after a campaign in which he's taken hawkish stands on Russia, Iraq and just about everything else—John McCain quickly emerged as Mr. Hot, a candidate who makes no apologies for his often merry mischief-making. (See Palin, Sarah H., selection of for further evidence.) With his measured responses to the news of the season and his steady insistence on projecting a cerebral image, Barack Obama came off as Mr. Cool, at once impressively intellectual and yet aloof.

The three tests of recent weeks—the vice presidential nominations, the conflict in Georgia and now the financial crisis—have raised, in a serious way not always evident in presidential politics, the key question: how would each man lead? Our view is that if you are among the 18 percent or so of undecided voters (the current figure in most national polls), we think you now have more than enough on which to decide. McCain and Obama see the world differently, and you can see how; they behave in their own skins differently, and you can see how. The drama of the autumn has served perhaps the noblest end we could hope for, shedding light on how each man would govern. McCain is passionate, sometimes impulsive and unpredictable; Obama is precise, occasionally withdrawn and methodical.

It would be comforting, of course, if there were such a man as Mr. Just Right, but human nature is rarely so accommodating. Politicians, like the rest of us (only more so), tend to overcompensate. Obama cannot afford to be seen by voters as an Angry Black Man, but he sometimes appears calm to the point of passivity. At moments during the past two weeks of dizzying market gyrations and grim economic tidings, he seemed more like a bystander than a player. This may, in fact, have been the wise choice, both for the country and for his political fortunes. He understood that, by butting into the delicate negotiations between the White House, Treasury and Congress to shape a rescue package, a presidential candidate risked injecting politics and partisanship into a situation that demanded statesmanship and discretion.

On the other hand, McCain may have figured he had nothing to lose by plunging in. As his running mate, Sarah Palin, mangled her canned answers to Katie Couric and showed up on YouTube submitting to anti-witchcraft ministrations from a Pentecostal pastor, McCain was rapidly losing his postconvention bounce. McCain is an improviser and, on occasion, a hip-shooter. A former Navy pilot, he has not always demonstrated the soundest judgment. (Of course, Obama enjoys a natural advantage from not having been in public life as long as McCain: you can't be criticized for making decisions when you haven't been in the arena to make them.) In his most recent book, "Hard Choices," McCain describes how, on his last bombing mission over Hanoi, he heard the warning tone of an enemy SAM missile locking on to his plane. Bravely, or rashly, McCain did not take evasive maneuvers but rather kept on flying straight in an attempt to deliver his bombs on target. The missile blew off his right wing, and he spent the next five years in captivity. Over the subsequent years, mostly spent in politics, McCain has learned to "jink and juke," in pilots' parlance, but he sometimes still demonstrates a willfulness that can be admirable, or just foolhardy.

Watching McCain swoop and veer over the past two weeks has been enough to induce vertigo, even among his admirers. He began by saying that the "fundamentals" of the economy were "strong" and then, ridiculed by Obama, declared that the economy was "in total crisis." He took an angry populist tone against Wall Street and the regulators and proposed a 9/11-style commission to investigate what had gone wrong. He said if he were president, he would fire SEC Chairman Chris Cox. Informed that the president cannot fire the head of the SEC, McCain pronounced Cox to be a "good man," while still calling for his resignation.

Obama, meanwhile, kept his statements about the crisis measured, citing principles that should be taken into account in any bailout package but not offering a grand explanation for why one was needed. Throughout, he was quietly talking to Hank Paulson on a daily basis and grew to like Bush's Treasury secretary so much that he told CNBC he was thinking of keeping him on for at least a transition period.

A lifelong admirer of Theodore Roosevelt, McCain likes to be "in the arena," which may be why he asked the White House to summon a meeting of all the principals last Thursday—Republican and Democratic Hill leaders, top administration officials and the two presidential candidates.