Iowa and New Hampshire are out, though they may not go down without a fight. South Carolina and Nevada are in.

The Democratic National Committee formally approved sweeping changes to the party’s 2028 presidential primary calendar on Saturday, putting states that are more racially diverse at the front of the line.

The order in which states vote typically plays a significant role in shaping the presidential primary — influencing both what issues are discussed and who ultimately emerges.

Party officials set South Carolina first on Jan. 22, 2028, followed by Nevada (Feb. 1), New Hampshire (Feb. 8), New Mexico (Feb. 15), Michigan (Feb. 22) and Virginia on (Feb. 29).

The new calendar represents a sea change from past competitive primaries. For decades, Iowa and New Hampshire, two states with largely white populations, had started the process. Now, two southern states and two Western states will be among the earliest contests, which is likely to expand the influence of Black and Latino voters. “Six states, different regions, different communities, different experiences but together as one our road map to the White House,” Ken Martin, the DNC party chairman, said in a speech to the party on Saturday.

The earliest states will play an outsize role in winnowing what is expected to be an expansive field of candidates. The order was officially set by a vote of the D.N.C. membership at a meeting in Austin, Texas, on Saturday.

After those first six states vote, each on their own day, a range of states will vote on Super Tuesday in early March.

The party’s new rules include stiff penalties for states that hold primaries in violation of the calendar, and for any candidates who might campaign in those states. But some uncertainty remains, especially in New Hampshire, where a state law requires its primary be the first in the nation. The D.N.C. allows the state to hold a party-organized primary on Feb. 8.

Democrats in the state so far have resisted being relegated to third in line.

The party had tried to put South Carolina first in 2024, as well, but New Hampshire jumped the line. Former President Joseph R. Biden Jr. declined to appear on the New Hampshire ballot, so his supporters instead organized a write-in campaign, and the party eventually rescinded its penalties and seated the state’s delegates at the convention.

It is unclear when Iowa will hold a primary or caucus in 2028. The state has complained about the D.N.C.’s new calendar, and some politicians in the state have threatened to hold an early event anyway, citing their own state law, which calls for Iowa to caucus at least eight days before any other presidential nominating contest.

On Saturday, Rita Hart, chair of the Iowa Democratic Party, said the new calendar “excludes huge swaths of the country and the voters Democrats need.”

And she warned that it was still possible the process could be “thrown into chaos” and an “unwelcome distraction” for Iowa Democrats trying to win this year.

Jamie Harrison, the former D.N.C. chair and a former chair of the Democratic Party in South Carolina, made the case that, “We’re not erasing tradition. We’re building on it.”

Even with that uncertainty, potential 2028 candidates are already flooding into these early states. Pete Buttigieg, the former transportation secretary who now lives in Michigan, is headed to South Carolina for a political event next week. Gov. Gavin Newsom of California campaigned with Dr. Abdul El-Sayed, the progressive Democratic candidate running for Senate, this past weekend, after he won the nomination in Michigan. Representative Alexandria Ocasio-Cortez of New York had campaigned for Dr. El-Sayed ahead of the primary, and she also appeared in a campaign commercial for him.

Some leaders in South Carolina are eager for all the attention the state — and the issues that its voters care about — is now about to get. Iowa’s premier place for years had meant candidates would talk about agricultural issues and ethanol, for instance.

Black voters generally have been a moderating force in Democratic politics, so the early position of South Carolina could lead the state to have a similar effect. In the past, South Carolina played the pivotal role of anointing the candidate with the most momentum headed into Super Tuesday. Now Michigan and Virginia — which are bigger and more expensive to campaign in — are set to hold that power.

Political strategists in both the moderate and progressive wings of the party have pored over how the new calendar might play out. Mr. Buttigieg, for instance, carried Iowa in 2020, but now that state has fallen out of the early slate. Senator Bernie Sanders, a leading progressive, carried New Hampshire in both his presidential runs, but there is a debate over whether that was just ideological alignment or how much his decades representing nearby Vermont may have given him a boost.

Mr. Biden had placed South Carolina first in the calendar in 2024, elevating the state that delivered him the nomination in 2020 after bruising defeats in Iowa and New Hampshire. But it was far from certain that the state would keep that slot headed into 2028.

South Carolina had a fierce fight for the leadoff spot with Nevada, an important general election battleground.

The final order — which also includes New Mexico and its large Latino population — has received mostly positive reviews from Democrats as fair and geographically balanced. The biggest complaints have come from the Midwest, which now has only one state among the first six, Michigan, and it is only fifth.