The chairman of the Democratic National Committee predicted yesterday that two-thirds of the Democratic senators and representatives will be made uncommitted delegates to the 1984 national convention and that Iowa and New Hampshire will be nudged into delaying their early-bird caucus and primary until after March 1.

Charles T. Manatt, the party chairman, told a group of reporters he believed 250 to 300 elected officials would get credentials as delegates in 1984 without the requirement of stating their candidate preference and that all the delegate-selection decisions will be forced into a roughly 100-day period starting March 1, 1984.

Manatt said that states that try to schedule unofficial presidential straw votes or preference polls before March 1 would be penalized on their convention hotel and floor seating assignments.

Manatt expressed these predictions in telling reporters his "hopes" for the decisions of the party commission on presidential nominations, headed by North Carolina Gov. James B. Hunt Jr.

In a telephone interview, Hunt said, "It's a pretty independent commission and we have lots of opinions in there." Other commission sources said they expected heavy debate on some of the issues Manatt discussed, and the party chairman later had a spokesman call reporters to make it clear he was "not trying to influence the outcome" of the commission discussions.

Nonetheless, Manatt's comments gave the first public clue on the possible outcome of the latest Democratic rules revision.

The House Democratic Caucus has proposed selecting two-thirds of its members as unpledged delegates. Manatt said he hoped that that number of representatives and senators would be given that status, but said nothing was settled on whether they would be selected by the congressional caucuses or by their home-state party organizations.

The AFL-CIO has suggested that up to 30 percent of the 1984 delegates be unpledged elected and party officials. But Manatt said he thought the desired number of governors and members of Congress would take no more than 7 percent of the seats and that others, if singled out for preference, would likely be bound by the results of the candidate caucuses and primaries in their states.

As for shortening the delegate-selection season, Manatt said there was a way to accommodate the special problems of Iowa and New Hampshire. Iowa began the 1980 parade with its Jan. 21 precinct caucuses. Manatt said he had discussed with Iowa party leaders delaying the start of the presidential process until the county conventions, which last time were held on March 8 and 9.

New Hampshire held the first primary on Feb. 26, 1980, and has a law requiring its primary to be at least a week ahead of any other state's.

"They can still be first by being on March 1," Manatt said. He conceded, however, that under his plan New Hampshire might have to share that date with other states.

Walter Dunfey and Edward Campbell, the New Hampshire and Iowa representatives on the Hunt commission, said they were familiar with Manatt's preferences but were still planning to fight for exemptions for their states from the March 1 starting time.

In a related development, Manatt disclosed that the Democratic National Committee had protested last Friday the activities of a member of the staff of Source, a Republican National Committee publication, who was polling members of the Hunt commission on their candidate preferences and views of the delegate-selection issues.

Manatt said Ron Brown, the DNC counsel, was assured by his opposite number, Mark Braden, that the polling would stop. An RNC spokesman said yesterday that Source was polling in hopes of developing a news story on the Democratic commission members' views, since no votes had been taken on the issues.