A new generation is coming to the White House. Barack Obama, born in 1961, is technically a baby boomer. But his early years were straight out of Generation X -- abandoned by his father and, for a time, his mother; experimentation with drugs; a sense of drifting.

His two predecessors, both born in 1946, generally considered the first year of the baby boom, personified the two halves -- liberal and conservative -- of their generation, and both had characteristics that those on the other side of the cultural divide absolutely loathed. Obama, in Boston in 2004 and in Grant Park on victory night, promised to take us above and beyond these divisions.

The constituency Obama assembled during his campaign has a decided new-generational tilt. The Edison-Mitofsky exit poll tells us that Obama carried voters under age 30 by a margin of 66 percent to 32 percent. On the flip side, by my calculation, he won voters 30 and over by just 50 percent to 49 percent. That means that he won by a larger percentage among young voters than any president, and that among voters older than that, he may or may not have carried states with a majority of electoral votes. In retrospect, the only winning Republican strategy would have been to pass a constitutional amendment raising the voting age to 35.

This is the third time in a century that we have seen such a generational change in the White House. From 1933 to 1961, we had presidents born between 1882 and 1890. From 1961 to 1993, we had presidents born between 1908 and 1924. John Kennedy's inauguration marked the departure of the World War II commanders who occupied the White House for 28 years; Bill Clinton's the moving on of the G.I. generation after 32 years. Obama's will mark the passing of the boomers after only 16.

The advantage of a new generation is that it brings fresh ideas and perspectives, a greater sense of possibility and none of the weariness of fighting the same old battles over and over. The disadvantage is that it lacks experience and doesn't know the lessons of the past.

Obama does make reference to history, especially to distant figures like Abraham Lincoln and FDR. But like Tony Blair, he is given to rhetoric that suggests history begins anew with his installation in office. "This was the moment," Obama said on June 3, after the last primaries, "when the rise of the oceans began to slow and our planet began to heal." He is promising more than King Canute.

There is a tension here between the "hope and change" Obama promises and the issues he and the leading advisors he has recruited will face. On foreign policy, we have Hillary Clinton at State and Robert Gates at Defense. Our troops in Iraq will be withdrawn, but not completely, it seems -- and after something like victory, rather than the defeat and disgrace that so many Democratic politicians and voters craved as long as the hated George W. Bush was president. Less change than many hoped for.

On the economic team, we see Lawrence Summers and Paul Volcker among those tasked with handling economic problems -- a collapse of credit, deflation -- that no one anticipated as recently as six months ago. None of Obama's sophisticated economists, if they were starting from scratch today, would recommend the stands Obama took during nearly two years of campaigning: higher taxes on high earners, moves toward protectionism. Those were Herbert Hoover's policies in the 1930s.

So now we will see, as we have in recent months, much improvisation. We have had and will have in key places the men who probably know as much about deflation and financial markets as anyone else on Earth. Yet we have the sinking feeling the old team hasn't been batting 1.000 and that the new team won't be able to, either.

Much of the energy that fueled the Obama campaign came from a visceral hatred of Bush and all his works. The relaxed acceptance that those on the Democratic left have given Obama's moderate appointments and skinning back on liberal promises suggests they're satisfied, for now, with Bush's removal. But in time, they and the rest of us will be making more critical judgments on how this new-generation president is doing. Change is not all we hope for.