James Christian, a Washington lawyer and former Capitol Hill aide, is being touted by local Democrats as the probable successor to Ivanhoe Donaldson, who intends to step down tonight after one term as chairman of the D.C. Democratic State Committee.

Christian wasted little time in enlisting support for the post, after Donaldson confided in friends that he wouldn't seek a second term because of the demands of his job with E.F. Hutton Inc. and legal problems stemming from a grand jury investigation of Donaldson's activities while he served in Mayor Marion Barry's administration.

"There's no question we're going to win," said Joseph Carter, the alternate Democratic national committeeman from Ward 4, who has helped organize Christian's campaign.

Larry Weston, executive director of the Metropolitan Washington Planning and Housing Association, and Joslyn N. Williams, president of the AFL-CIO's Metropolitan Washington Council, are among a handful of Democrats who have been mentioned as possible candidates.

But Christian and his allies outhustled Weston in lining up support, according to some party officials. And Williams encountered resistance from members who thought it was inappropriate for the city's chief labor leader to also head the local party.

A few Democrats are upset about Christian's candidacy because he is an ex-officio member who didn't have to run in a city election for a seat on the state committee. But with Donaldson's and Barry's unofficial blessing, Christian should have little trouble winning election at the state committee's annual reorganization meeting tonight.

Christian, 37, a Harvard Law School graduate, was a deputy counsel to the House District Committee and the chief legal counsel to the D.C. City Council before going into private practice in 1979. He has also served as a legal counsel to the Democratic state committee.

There has been growing speculation that Sharon Pratt Dixon will relinquish her post as D.C. Democratic national committeewoman, throwing open another key local party post. Dixon, an executive with the Potomac Electric Power Co., was elected treasurer of the Democratic National Committee in January and recently indicated that she felt it didn't make sense to continue holding both party positions.

However, Dixon said this week that she has been lobbied by some committee members to continue as national committeewoman, and she has postponed making a final decision until early fall. Daria Winter, vice chair of the party and the alternate D.C. national committeewoman, is in line to replace Dixon if she steps down as national committee woman.

Donaldson, a former deputy mayor and a longtime political adviser to Barry, ousted incumbent Theodis (Ted) Gay a year ago by an impressive 2-to-1 margin.

While many Democrats were excited by the prospects of the high-powered Donaldson taking charge of the obscure and largely ineffectual local party, some feared he would make life miserable for those who didn't see eye-to-eye with Barry. Gay warned the membership that with Donaldson as chairman, the party would become "an organization that serves the political ambitions and interest of a select few."

But Donaldson gained the respect and support of most state committee members with a largely evenhanded style and unquestioned skills as a political organizer and fund-raiser. The state committee's annual Kennedys-King Dinner, which was held May 2 at the Hyatt Regency Washington, drew a record 1,100 guests and netted the party about $31,000, according to party officials.

For years, the party operated quietly on the sidelines, rarely venturing into the limelight. Donaldson began to change that by holding a forum on Democratic Party issues and encouraging the state committee to take stands on local issues, including rent control and proposed telephone rate increases.

"Ivanhoe has been very good in terms of not only being responsive to issues but actually taking the lead," said Mark Plotkin, a committee member from Ward 3. "My concern is that Christian isn't going to be as much of an activist."

Christian insists he would continue Donaldson's practice of pushing the party to take strong stands.

"We have to move the party to be an aggressive force on local issues affecting the District of Columbia," he said. "We're always reacting. We have to move forward with an agenda."