Sixteen years ago, in a "Saturday Night Live" sendup of the 1988 presidential debates, Jon Lovitz -- playing Michael Dukakis -- replied to a windy diatribe by Dana Carvey's George H.W. Bush with the exasperated remark: "I can't believe I'm losing to this guy."

Once again, it's presidential debate season and once again Democrats can't believe their candidate is losing to a Bush -- especially this one. After all, George W. Bush failed to win the popular vote (and every president elected in that way has lost reelection); he stands to become the first president since Herbert Hoover to oversee a net loss of private-sector jobs on his watch; and he must defend a preemptive war against Iraq that was based, at least partly, on evidence now known to be wrong. To top it off, polling by CBS News-New York Times this month shows that half the electorate believes the country has "pretty seriously gotten off on the wrong track," and a Washington Post-ABC News poll shows that half of registered voters are "dissatisfied with the way things are going" in the United States.

Why then, Democrats wonder, with just five weeks before Election Day, isn't Kerry cleaning the president's clock?

After all, he has repositioned his campaign to hit back against the Swift Boat Veterans for Truth, the technically independent group that has tried to sink Kerry with a series of factually suspect television ads that questioned the Democratic nominee's conduct in Vietnam. And Kerry has responded to those who grumbled that he has never made the case against Bush, mistakenly believing that voters who are dissatisfied with the way things are will naturally blame the president. Just this past week, for instance, he articulated a forceful criticism of Bush's conduct of the war in Iraq and of the war on terrorism.

All of these are good strategic moves, but it's not enough to say, as though in a race for president of the high school student body, that W stands for wrong. To win this race, Kerry needs to stop focusing on Election Day and start thinking about his would-be presidency's last day. What does he want his legacy to be? When sixth-graders in the year 2108 read about the Kerry presidency, what does he want the one or two sentences that accompany his photo to say?

The need for a grand, yet simply communicated vision is what separates running for president from running for any other office. Unlike in a race for senator or governor, launching a devastating attack against one's opponent or simply insisting that you're on the "right" side of a series of issues is not enough to win the White House. The office of president of the United States is different from the governing seat of almost every other country in the world in that its occupant is both head of the government and head of state. A candidate must not simply display a command of policy minutiae and legislative process, but also a grasp of the office's symbolism and an understanding of the nation's historical moment.

Think back to 1976. On the campaign trail, Jimmy Carter promised a country jaded by Vietnam and Watergate a "government as good as our people are." Carter's vision and the legacy he wanted to leave were summed up in that one sentence. And even though he was just a former one-term governor from Georgia, that clearly defined vision -- and his own personal embodiment of it -- propelled him to the presidency.

Four years later, Ronald Reagan told a nation battered economically and losing strength and influence abroad that America did not have to accept this fate. As he explained in his acceptance speech at the GOP convention: "The American people, the most generous on earth, who created the highest standard of living, are not going to accept the notion that we can only make a better world for ourselves by moving backwards ourselves." He wanted to "recapture our destiny," so that America could walk tall again.

During the campaign, Carter attacked the details of Reagan's agenda relentlessly. Yet on Election Day, Reagan's specific plans for rejuvenating the economy and fortifying the national defense were inconsequential compared with the sense of optimism and a new beginning that he projected. And if you listened to the eulogies at Reagan's funeral this year, lifting up America -- or bringing about a "morning in America" -- is what his legacy ended up being.

In 1992, Bill Clinton ran for president to "provide leadership that will restore the American dream, that will fight for the forgotten middle class, that will provide more opportunity, insist on more responsibility, and create a greater sense of community for this great country." From the announcement of his candidacy in October of 1991 until he left office in January of 2001, Clinton's policy agenda can be explained as fulfilling at least one of these three goals: opportunity, responsibility and community.

Yet it was the other part of the Clinton legacy, the personal scandals, that set the stage for his successor. The rationale for the presidency of George W. Bush -- the legacy that he wanted to leave -- was that he would "restore honor and integrity to the White House." Bush, the "compassionate conservative," proclaimed no intention of radically altering the policy course of a prosperous country at peace. (Remember that he and Al Gore argued about how much and in what ways to cut taxes, not whether it was a good idea.) Instead, having redeemed his own admittedly aimless life at 40, Bush would also redeem America.

Then, the attacks of Sept. 11, 2001 happened, and Bush decided to embrace a different potential legacy: He would become the "war president" who took on global terrorism and Saddam Hussein after too many dangerous years of half-hearted reactions to both. Now, as Bush told the nation upon accepting his party's renomination earlier this month, "I wake up every morning thinking about how to better protect our country. I will never relent in defending America -- whatever it takes."

This simple explanation of what he wants his legacy to be is what is keeping Bush in the race. It addresses the most important issue to voters -- security -- and underscores the leadership qualities that Americans want in a president but that can't be conveyed through policy proposals. And it seems to be working. According to the latest Washington Post-ABC News poll, by a margin of 53 percent to 37 percent, registered voters trust Bush more to handle the situation in Iraq, and by a margin of 57 percent to 35 percent they trust the president in the war against terrorism. On top of that, 58 percent of those polled believe Bush is a strong leader; only 31 percent say the same about Kerry.

What's holding Kerry back is that he has yet to put forward a compelling legacy to compete with Bush's. Kerry won his party's nomination by running as the "real deal," who in a crowded field was the only Democrat who could beat Bush. At the Democratic convention, the argument was that Kerry would make America "strong at home and respected in the world." While it was a contrast to Bush's vision, when the sole rationale put forward for Kerry's foreign policy leadership -- his service in Vietnam -- was impugned by Swift boat veterans opposing his candidacy, this became an empty slogan. When he reported for duty, as he put it at the convention, Kerry chose not to complete his Vietnam story -- the different courage needed to criticize the war after returning home and the life of public service that ensued -- and tell voters what it all means today. For nearly two months, the Bush campaign was free to fill in those blanks for him.

It isn't that Kerry lacks an agenda; in fact, he has a popular one. And last week, with a new team of advisers, Kerry rolled out a sharp critique of the president's wartime leadership to undermine Bush's claim to his potential warrior legacy. In a speech at New York University last Monday, Kerry argued that Bush "has not told the truth to the American people about why we went to war and how the war is going." Because of this, he said, "the world is a more dangerous place for America and Americans."

This is a good start (and hopefully not too late). In addition to this critique and an explanation of what Kerry would have done differently, he also needs to flesh out what he would do -- not just in Iraq, but with his presidency. Already, the contours of what his legacy could be are becoming clear: He will be the adult who cleaned up the mess the careless and reckless Bush has made. This is a natural fit for Kerry's biography and personality. As Kerry said in his speech last week, "It is never easy to discuss what has gone wrong while our troops are in constant danger. . . . I know this dilemma firsthand. After serving in war, I returned home to offer my own personal voice of dissent. I did so because I believed strongly that we owed it [to] those risking their lives to speak truth to power. We still do."

This truth-telling was also a hallmark of Kerry's Senate career, one highlighted by investigations that took on both Republicans and Democrats. Finally, as we approach the presidential debates, Kerry's august demeanor and languorous seriousness can be an asset if framed as part of a man who will repair the damage that an intemperate Bush has done to the country's economy and security. And if Kerry is allowed to be Kerry, voters will sense his authenticity -- the most potent rebuttal there is to the charge of "flip-flop."

Kerry now has three debates and 37 days to persuade voters to give him a chance to add his legacy to the history of America. If he fails, he could end up like the last unsuccessful Democratic nominee from Massachusetts: remembered mostly for his contribution to the legacy of late night TV humor.

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Kenneth Baer, former speechwriter for Vice President Al Gore, is the author of "Reinventing Democrats: The Politics of Liberalism from Reagan to Clinton" (University Press of Kansas, 2000) and founder of Baer Communications, a Democratic consulting firm.