Washington ? Call it affirmation or reaffirmation, the midterm election has given a powerful boost to President Bush, the conservative agenda and the long-term prospects of the Republican Party. By retaking the Senate, increasing their majority in the House and strengthening their grip on their Electoral College base in the South, the Bush-led Republicans achieved substantially more than most observers ” myself included ” had thought likely.

For the past two years, ever since he won the White House while losing the popular vote and having to turn to conservative justices on the Supreme Court for confirmation of his victory, Bush has struggled against the label of an “accidental president.”

But the support he won by his sterling performance after the terrorist attacks of Sept. 11, 2001, has endured, and he showed on Tuesday that he could convert that popularity into votes for his fellow-partisans. That is the most powerful leadership tool any president can possess.

In hindsight, it now appears that it was the Democrats who had gained from political accidents, enjoying their shaky Senate majority only because a sympathy vote for an airplane crash victim in Missouri was followed by a fit of pique from an iconoclastic Vermonter.

In the absence of exit polls, it is impossible to say definitively whether Tuesday’s Republican victories came from changing voters’ minds or from altering the makeup of the electorate. It was probably a bit of both.

Republican pollster Bill McInturff, who did his own election night survey, says that the Republicans may have beaten the Democrats at the turnout game ” especially in the South. That would not be a surprise. The voter interviews my Washington Post colleagues and I did in mid-September showed us that Bush supporters were more highly motivated at that point than Democrats.

The Republicans we met had a clear reason to back Bush; it was their way of demonstrating their loyalty to the commander in chief of the war on terrorism. Back then, Democrats had not received any similarly clear and compelling signal from their party leadership. And in the end, the issues the Democratic hierarchy hoped would energize its constituency ” the shaky economy, corporate greed, runaway drug prices ” never were given enough of a partisan dimension to work.

The election demonstrated more than Bush’s personal support. A striking feature was the success of Republican incumbents at all levels. Not a single Republican governor running for re-election lost. The only incumbent Republican senator defeated was Tim Hutchinson of Arkansas, whose divorce and remarriage had severed his bonds with his religious conservative following. And in House races, only two Republican members were defeated.

Clearly, after such an election, Republicans will feel emboldened to push ahead with the agenda that was often thwarted when Vermont Sen. Jim Jeffords’ switch to independent status gave Democrats their temporary control of the Senate.

As I have frequently noted, Bush is the opposite of a status-quo conservative. Even without the benefit of a clear electoral mandate, he pushed for and largely achieved sweeping and even radical changes in education, fiscal policy, defense and foreign policy doctrine. He also proposed to shift the boundaries in church-state relations, change Medicare and Social Security, and alter the makeup of the judicial branch by determinedly conservative appointments.

A president who moved so boldly on a shaky political base will surely attempt far more now that his party is clearly in the ascendancy. Economic policy will be a major focus, as Bush presses to make the tax-cutting agenda more extensive and to lock in permanently the large rate cuts already on the books.

As against all this, the Democrats’ only consolation lies in the gains they made in governorships, adding Pennsylvania, Michigan, Illinois and Wisconsin to California, Virginia, North Carolina and New Jersey among the significant building blocks of the Electoral College.

In the short term, these governorships may provide more headaches than advantages. All of these states are facing severe budget crises, and the hard choices now will have to be made by Democrats. But over time, the opposition party will benefit from having a crop of capable and attractive leaders operating outside Washington, D.C.

There may not be a presidential contender among these governors, but they are potentially a pool of leadership for a party desperately in need of that commodity. The fecklessness of congressional Democrats ” who lacked the nerve to say what most of them really believe about either the Bush tax cuts or his path to war with Iraq ” made it easier for the president to look like the rare politician with the courage of his own convictions.

And that is why he is in command today.

” David Broder is a columnist for Washington Post Writers Group.