While claims of fraud by a major black contender may have marred the image abroad of last week's Rhodesian election, the protests are regarded here - after two days of reflecton - as little more than political infighting between internal black leaders.

The two leading black contenders - the Rev. Ndabaningi Sithole and Bishop Abel Muzorewa - both used essentially the same tactics during the campaign and the voting itself to get out as many voters as possible for their rival parties.

As a result, most observers here believe Sithole's complaints of irregularities grow mostly from pique at the beating he took from Muzorewa, who is scheduled to become Rhodesia's first black prime minister.

At a press conference yesterday, Sithole alleged that he had reports of irregularities from "various regions across the country." He however, indicated that he was reserving final judgment until a special commission of inquiry looks into the evidence and testimony that he says will substantiate his charges.

For the moment, Sithole does not seem to have the courage of his stated conviction that the elections were "stage-managed" and full of "appalling irregularities." He is apparently unwilling to refuse to sit in the new government or to demand a new round of voting.

The allegations he has made could just as easily be leveled against him by Muzorewa if he persists.

Still, Sithole does have the power to become a spoiler of the general image that the Rhodesian government has apparently created abroad of the elections being relatively fair.

He expects the British and U.S. governments to reach a conclusion about the nature of the elections before deciding whether to grant the new government recognition and to lift economic sanctions.

"The British and Americans will have to decide that one," he replied to a question whether Washington and London should accept the elections.

In assessing Sithole's claims, observers here have been struck by the fact that he repeatedly said the campaign before last week's elections had been "free and fair" and even issued statements Monday afternoon still stating they were "free and clearly above board."

All indications are that Sithole changed his mind and tactics when be began recieving reports from "various regions across the country" that his Zimbabwe African National Union was taking a trouncing. It finally got 14.5 percent of the votes, compared to Muzorewa's 67 percent, and wound up with just 12 seats in the new Parliament against 51 for Muzarewa's United African National Council.

Many resident foreign correspondents were surprised he did that well, for there were many indications during the campaign that Sithole was trailing Muzorewa badly and was resorting to tactics he has accused Muzorewa's party of employing.

Even if Sithole acted as a poor loser, he may be able to cast doubt on the honesty of the elections.

A Sithole spokesman said today that the party was collecting testimony from alleged victims and witnesses of irregularities and that a detailed report would be submitted, probably to the existing electoral Supervisory Commission.

He said the party had "plenty of concrete evidence" and that even some white election officers had volunteered accounts of the misconduct. He said the chief offenders were the district commissioners and their assistants and paramilitary auxiliaries of Muzorewa's party who had tried to pressure voters.

"The elections were not free or fair in any way," he said.

"The whole thing was a farce, a sham."

One of the main problems in the Sithole position is that Muzorewa's National Council can probably draw up a similar report of coercion by Sithole's 2,000 to 3,000 armed party auxiliaries. Both parties used their auxiliaries to "get out the vote."

The allegation that district commissioners took sides is a potentially more damaging issue that remains to be proven.

Sithole would seem to be in a bit of fix. He has nowhere to go, even as the loser. He said Tuesday that he intends to stay in the country.

It seems unlikely that either guerrilla leader outside the country, Joshua Nkomo or Robert Mugabe, has much use for Sithole after his poor showing at the polls.

Sithole might succeed in casting doubt abroad about the validity of the elections by pursuing his allegations, but the net effect may be to bring himself down along with the new Muzorewa-led government. CAPTION: Picture, Prime Minister-elect Abel Muzorewa, in robe, salutes backers in Salisbury. AP