The Democratic presidential primary-caucus schedule has gone through a wholesale reordering since the 2000 election, with candidates facing the most diverse and challenging series of early contests in at least two decades.

As always, the 2004 nomination process will begin in Iowa and New Hampshire, which will hold their contests in late January. But in contrast to four years ago, when there was a five-week gap between voting in those two states and the next round of events, at least a dozen states -- most of them small or medium-sized -- will hold primaries or caucuses in February.

Underscoring the wide-open battle among the Democrats, the schedule appears to favor no particular candidate, according to strategists in the campaigns, and offers the contradictory opportunities for a candidate who lost both Iowa and New Hampshire to revive his or her campaign the following week, or conversely, for someone to accelerate rapidly toward the nomination by riding the momentum of victories in Iowa and New Hampshire in subsequent states.

"This is completely different from 2000," said Tad Devine, a top adviser to Al Gore's presidential campaign and now an adviser to the campaign of Sen. John F. Kerry (D-Mass.). "The dynamic of this calendar and the multi-candidate field means there are many potential strategic options a candidate can seize on and play out to his advantage."

The new calendar means that in the period of a few weeks, candidates will be forced to campaign in states in every region of the country and in states where different parts of the Democratic base, from African Americans to Hispanics to organized labor, will emerge as the potentially crucial voting bloc.

Party officials see an additional advantage: The eventual nominee will get a head start in organizing and campaigning in swing states that will be crucial to the party's hopes of defeating President Bush in November 2004. Four years ago, Gore essentially won the nomination over former New Jersey senator Bill Bradley on the votes of Iowa and New Hampshire alone.

"The '04 calendar is more balanced than the 2000 calendar," said Josh Wachs, chief operating officer at the Democratic National Committee. "2000 had Iowa and New Hampshire followed by 16 states on one single day [five weeks later]. The calendar as it looks for '04 . . . is more spread out. It won't be decided after just three days of contests as it was in 2000."

One big piece of the puzzle fell into place this past week when the Michigan AFL-CIO voted in favor of holding that state's contest on Feb. 7. Led by Sen. Carl M. Levin (D-Mich.), some Michigan Democrats were pressing to schedule their contest on Jan. 27, the same day as New Hampshire, to protest the Granite State's protected status at the front of the calendar.

DNC Chairman Terence R. McAuliffe fought the proposal as a violation of party rules, which prohibit states other than Iowa and New Hampshire from holding events before February. The AFL-CIO action means the Levin forces will not have the votes to win approval of the earlier date. But it also means that Michigan, as the first of the major industrial states to hold a contest next year, will be one of the most important early battlegrounds in the nomination battle.

The timing of several other state contests remains in flux, but the Michigan decision sets up the following schedule:

* Jan. 19: Iowa.

* Jan. 27: New Hampshire.

* Feb. 3: South Carolina, Delaware, Missouri, Arizona, New Mexico and possibly Oklahoma.

* Feb. 7: Michigan and possibly Washington.

* Feb. 8: Maine.

* Feb. 10: Virginia.

* Feb. 17: Wisconsin.

* Feb. 24: Idaho.

* Feb. 27: Utah.

Then, on the first Tuesday in March, a dozen states, including New York, California, Maryland and possibly Ohio, will weigh in on what is likely to be the decisive day of the nomination battle.

(As a way to protest lack of voting power in Congress, D.C. Democrats have set their contest for Jan. 13, which would make it first. That date violates DNC rules, which could mean the D.C. delegation would not be seated at the national convention in July 2004; party officials hope to work out a compromise that will push the primary to sometime in February.)

Because of geographic proximity, Rep. Richard A. Gephardt (D-Mo.) is favored in Iowa, while Kerry of Massachusetts is favored in New Hampshire. But advisers to Sen. John Edwards (D-N.C.) and Sen. Joseph I. Lieberman (D-Conn.) say the calendar gives them options for a quick recovery that Bradley did not have after he narrowly lost New Hampshire to Gore four years ago.

Edwards will be under pressure to win his neighboring state of South Carolina, which of all the states with contests Feb. 3 is likely to become the most significant battleground; and with Sen. Bob Graham (D-Fla.) in the race, Edwards cannot campaign as the only southerner.

Lieberman in particular is trying to take advantage of the new schedule, first by staking a claim on Arizona as a state that could provide him with his first victory of 2004 and by encouraging Democrats in Oklahoma, where he believes his centrist views will play better than in Iowa or New Hampshire, to move their primary from Feb. 17 to Feb. 3.

With so many contests coming so quickly, every campaign will be stretched to decide how much candidate time and campaign money to invest in one state vs. another. Arizona is not a large state, but the Phoenix media market is expensive. A bad bet could prove costly.

Strategists for the candidates differ on who may be helped most by the changes. A Gephardt adviser said the new system will "help people who have momentum over people who have money." That could benefit former Vermont governor Howard Dean, who lacks the fundraising strength of other candidates and who counts on strong showings in Iowa and New Hampshire to give him a boost. But an adviser to another candidate said: "It will become advantageous to a candidate who can run a national campaign and who can do well in the early states. I think there will be tremendous acceleration coming out of New Hampshire and Iowa."

Party officials see the new calendar as helpful in several ways. They believe it will assure that the nominee is selected by early March, will test candidates in a variety of settings and will energize many more Democrats earlier than in 2000.

"In the first four weeks alone, you have people competing in rural areas like Orono, Maine, to urban areas like St. Louis to suburban Phoenix to exurban Centreville, Va.," one Democratic official said. "It also allows different groups that are important to the party the ability to play a significant role in the nomination process: labor [in Michigan], African Americans [in South Carolina], Hispanics [in New Mexico], Native Americans [in Oklahoma]. More states count in the process, and that's a good thing."

Nine declared Democratic presidential candidates appeared at the Children's Defense Fund Forum on April 9.