A spate of rumors has descended on this city suggesting that one of the senior figures in the Soviet leadership, Politburo member Grigori Romanov, has come under a poltical cloud and that his future in the party is uncertain.

Romanov, 62, long has been viewed as a rival to the new Soviet leader, Mikhail Gorbachev. At the time of Konstantin Chernenko's death in March, the two men were the only Politburo members who were also secretaries of the Communist Party Central Committee, a combination of positions that was a traditional prerequisite for anyone aspiring to become the leader of the Soviet Union.

Speculations about Romanov's long absence from public life and possible personnel changes have taken on an edge of urgency as the Central Committee, the party's top policy-making body, prepares to meet Monday for its regular session.

Romanov was last seen in public on May 9, when he attended Red Square ceremonies commemorating the 40th anniversary of Nazi Germany's defeat in World War II. Since then, his name has appeared only once in the Soviet press, on the list of mourners following the death of Marshal Kiril Moskalenko on June 17.

There have been no official explanations for Romanov's absence. Soviet officials privately said he was ailing.

But travelers arriving here from Pitsunda, on the Black Sea, reported seeing Romanov there on vacation earlier this month.

According to the travelers, Romanov was met upon arrival in Pitsunda by a local party official rather than by Eduard Shevernadze, first secretary of the Georgian Soviet Republic and alternate Politburo member, as is normally required by protocol.

In the absence of authoritative information, it was not possible to assess these reports and rumors.

But there have been indications during the past few months that Romanov's influence was on the wane and that he was no longer a member of the inner circle in the Politburo.

Since he vanished from public view, rumors have begun to circulate that after Chernenko's death, Romanov had sought actively to block Gorbachev's election to the post of general secretary of the Communist Party, the country's top political position. One rumor, which also could not be confirmed, had Romanov advancing the candidacy of Politburo member Viktor Grishin to succeed Chernenko.

Rumors of alleged indiscretions by Romanov have been revived increasingly during the past few weeks. One rumor involves a wedding party for his daughter, for which Romanov borrowed Catherine the Great's dinner service from the Hermitage Museum. In the revelry, it is said, some of the historic china was broken.

Another rumor has Romanov allegedly violating party rules by taking up residence with a young woman, a well-known Leningrad pop singer.

Yet another and more recent rumor has the couple straying into Finnish waters aboard Romanov's yacht and causing an international incident.

It seems significant, according to diplomatic observers, that the authorities have done virtually nothing to dispel the rumors that Romanov's political standing may have been tarnished.