The House Rules Committee cleared the way yesterday for a showdown over the House assassinations inquiry amid a sudden outburst of demands for the chief counsel Richard A. Sprague.

"I think this resolution is in serious trouble on the House floor," Rep. Morgan Murphy (D-Ill) warned members of the Assassinations Committee at a hearing before the Rules Committee.

Although Speaker Thomas P. (Tip) O'Neill has promised "wholehearted support" for keeping the investigation alive, Murphy said advocates of the inquiry were seriously underestimating "the feelings of the members of the House" about Sprague.

"I think you ought to get your own man in there, Murphy warned the newly installed Assassinations Committee chairman, Louis Stokes (D-Ohio). "What he can do to Henry, he can do to you."

Rep. Henry B. Gonzalez (D-Tex.), the former chairman whom Murphy was talking about, underscored the mood in a bitter speech on the House floor about how he unsuccessfully tried to fire Sprauge last month. He said he was deserted by House Democratic leaders and committee colleagues, and blamed it at least partly on racial discrimination.

"I think I have been treated shabbily," Gonzalez declared. "I think that if my name were Jones or O'Brien or Rosenthal or George Washington Carver or Martin Luther King, I would not have been treated so shabbily."

The Texas Democrat held the floor for more than an hour with a chapter-and-verse reciation of his efforts to restore order to the committee's finances.

The day after he ordered Sprague's dismissal, Gonzalez said, Majority Leader Jim Wright (Tex.) assured him, "Well, fella, we're with you're right."

I don't think how anybody could interpret that," Gonzalez said. "I took it as support." But it soon disappeared when the rest of the committee remained solidly behind Sprague. Gonzalez quit the chairmanship and the committee on March 8.

With heavy sarcasm, Gonzalez at various points imitated the voices of Reps. Shirley Chisholm (D.-N.-Y.) and Richardson Preyer (D.-N.C.) speaking at a Rules Committee hearing in January, described Rep. Richard Bolling (D-Mo.) as "the great rajah of the Rules Committee," and called Del. Walter E. Fauntroy (D.-D.C.) "the vizier of Washington."

The Rules Committee voted 9 to 4 to set up a floor vote Wednesday on continuing the investigations into the murders of President Kennedy and Martin Luther King Jr. for the remainder of the 95th Congress. Two other Rules Committee members, Murphy and Rep. John Young (D-Tex.), voted "present."

Appointed chairman March 8, Stokes said he inherited a committee staff that was marking time with "almost no stationary, almost no supplies" and was "unable to travel" or even make a long-distance phone call. He strongly urged keeping the investigations going past their current March 31 expiration date and submitted a 14-page report indicating some of the "leads" the committee is pursuing.

The information, however, smacked of twice-told tales. In one passage reminiscent of former New Orleans District Attorney Jim Garrison's celebrated investigation, the committee said it is "actively pursuing several new leads which indicate that Lee Harvey Oswald was associated with CIA-supported anti-Castro groups.

Raising the persistent specter of a "false Oswald," the committee said those same "leads" also "suggest" that Oswald's "reported pro-Castro activities" and his "alleged" trip in Mexico City might have been deliberately designed to mask his CIA-supported anti-Castro associations.

Strokes insisted at yesterday's hearing that the inquiry was running smoothly now with Gonzalez gone. The new chairman maintained that Sprague had satisfactorily countered all the charges against him at a secret committee meeting recently.

Murphy noted that Gonzlez was not present when the questioning of Sprague was conducted. "We're taking Sprague's word ove Gonzalez' word, as I understand it," Murphy said. Citing Gonzalez' speech on the House floor earlier in the afternoon, Murphy said he was especially concerned about a charge that Sprague had forbidden committee staffers to furnish payroll information to committee members.

Stokes said that Sprague "has offered a number of times to step aside if it would be of assistance to the committee," but the committee remains solidly behind him

"I think you ought to accept that offer," Murphy said.