A former race track lobbyist today challenged the prosecution's version of a crucial 1972 hotel room meeting at which Maryland Gov. Marvin Mandel allegedly helped his friends promote legislation benefiting Marlboro Race Track.

The government's contention that Mandel sat in the private suite of co-defendant W. Dale Hess and helped tally votes on the legislation is pivotal to proving that the governor knew of his friends' secret ownership of the track.

Richard Rombo, a former Pimlico Race Course lobbyist, testified for the defense today that Mandel discussed the legislation only in passing at a "social affair" in the hotel room.

Rombro contradicted the previous testimony of Pimlico co-owner Nathan Cohen by claiming that he (Rombro) rather than Mandel, directed a crucial discussion about how to push through the 1972 race track consolidation bill.

That Annapolis Hilton Inn discussion, held the last week of the 1972 legislative session had been portrayed by Cohen as one where Mandel pulled out rosters of legislators and tallied votes on the pending "race track consolidation bill" that would have dramatically increased the value of Marlboro.

Rombro testified, "When the governor was getting ready to leave . . . either Mr. Hess or I asked about the consolidation bill. The govenor said he though it would have trouble."

Rombro then testified that he, not Mandel, took out a roster of legislators and for no more than five minutes they discussed who would vote in favor of the measure.

Cohen's previously unchallenged testimony is significant in the prosecution's case charging Mandel and his five codefendants with scheming to defraud the citizens of Maryland through an exchange of benefits. Mandel, the prosecution alleges, recieved $850,000 worth of gifts and favors from Hess, Harry W. Rodgers, William A. Rodgers, Irvin Kovens, and Ernest N. Cory Jr.

For these favors, the multicount indictment charges, Mandel lobbied for legislation that would have brough windfall benefits to the Marlboro Race Track, then allegedly secretly owned by the friends. All but Kovens have later acknowledged their ownership.

After almost two years of silence about these and other allegations, Mandel is scheduled to testify on his own behalf Thursday. That will conclude the defense presentation of Mandel lawyer, Arnold M. Weiner.

Mandel is expected to testify today on the 1972 legislative session covered by Rombro. Rombro said that when he lobbied for Pimlico he was told by Cohen that he would "work with" Hess, but he was note told that Hess or the other defendants were secret owners of the Marlboro track.

The dinner at Hess' Annapolis Hilton Hotel suite was a social affair, Rombro testified, not a work session as Cohen had testified.

He arrived late but in time for dinner and the repartee was about old battles fought in other legislative sessions, "the stories ex-legislators tell when they get together," Rombro testified.

The serious business of devising new amendments and strategies for the consolodation bill did not take place until the governor left the suit, Rombro testifies, and it was done by Cohen and himself.

Rombro, in a series of questions posed by Weiner, flatly denied that the govenor was part of "anything resembling a meeting" or that he gave any instructions on how to proceed with lobbying.

"He didn't and he wouldn't", Rombro said.

An admitted Democrat partism who has contributed to Mandel's campaigns as well as being an active lobbyist for other clients, Rombro said he only lobbied that one year for Pimlico although his firm still represents the race course as it has done for 10 years.

Under cross-examination by Assistant U.S. Attorney Ronald S. Liebman, the lobbyist admitted that he had come late for the dinner and may have missed any earlier discussions. But Cohen had specifically testified, as Weiner brough out later, that the tallying of potential votes came after eating, when the men pushed away the table and got to work.

THomas Hunter Lowe, Former Maryland House Speaker now a Mandel-appointed jusge of the Court of Special Appeals, testified today on his major role in that legislative session as well as the Ray's Point real estate venture that figures as one of the anti-racketeering counts in the government's indictment in the case.

Lowe upheld the defense's argument that, as speaker in 1972, he kept an independent posture and did not collaborate with the governor in the sucessful over-ride of a veto that led to windfall profits for the Marlboro Race Track.

At the same period Lowe was a partner with Mandel and cofedants Hess and the Rodgers brothers as well as Cohen to purchase a farm on Ray's point on the Eastern Shore for development.

Since that perios from late fall of 1971 to late spring of 1972 encompassed both the legislative manuevers as well as the purchase of Marlboro and Ray's Point, the prosecution asked Lowe repeatedly how he could not know of the secret ownership of the track by men who were his business partners.

Lowe said he bowed out of the Ray's Point transaction because he began feeling uneasy when he was kept out of business decisions that affected his financial liability. Besides, he testified, he did not trust Hess from whom he wrested the majority leader's position in the House some years before.

Lowe substantiated part of the prosecution's case by testifying that the Ray's Point farm was purchased as a profit-maing venture. Madel had claimed that he was interested in it only as a property for a retirement home.