One month ago, nationalist leader Joshua Nkomo returned from exile as public enemy number one to whites and a leader of a minority African tribe with seemingly little chance to become prime minister -- a goal he had sought for 30 years.

Today, less than two weeks before election of a black-majority government, the rotund veteran of guerrilla warfare and political infighting has become the candidate most likely to forge a coalition among warring parties to gain leadership of an independent Zimbabwe.

Both the British colonial administration and parts of the white establishment -- which has reviled Nkomo particularly since the downing of two Viscount airliners by guerrillas -- appear to be quietly encouraging Nkomo's bid as an alternative to his fellow guerrilla leader, Robert Mugabe, an avowed Marxist.

Nkomo has begun to put some distance between himself and Mugabe, 51, who is expected to win the most seats but far from a 51 seat majority in the Feb. 27-29 election.

The blacks are to hold 80 seats in the 100-member house. The results announced today in the whites' election of their members yesterday showed former prime minister Ian Smith's Rhodesian Front won all 20.

Nkomo, 62, has maneuvered into the position of being the likely kingmaker, if not the king, so long as he finishes second ahead of the former prime minister, Bishop Abel Muzorewa, as expected.

Nkomo and Mugabe have a driving ambition to be prime minister. Unless Nkomo can outpoll Mugabe, an unlikely event because of his narrow tribal base, he can best win power in alliance with Muzorewa, 54, whose fortunes appear to be declining daily, and Smith.

On the surface, such an alliance would seem bizarre since the parties have exchanged recriminations for years. But Nkomo and Smith have the political clout over their parties to pull it off and bring Muzorewa along.

"The prospect of power," a British official said, "can do wonders for the ability to compromise."

Even such a compromise, however, could easily fall apart under the expected pressure to horse-trade in the aftermath of any unclear election result.

Although Nkomo's Patriotic Front party officials describe Mugabe publically as their "natural" ally, Nkomo has dropped subtle hints that all is not well in the relationship with his erstwhile partner.

Nkomo has brought forward party workers to complain about intimidation. Privately, his officials make it clear that the complaints are often aimed at Mugabe's supporters.

Last weekend, Nkomo told a political rally that the voters should not elect somebody who could turn out like Ugandan dictator Idi Amin. He did not elaborate in English but chuckled and used the Shona word for rooster, which is Mugabe's party symbol.

Nkomo and Mugabe met this week for the first time in almost two months. Nkomo said they discussed "very serious issues." Mugabe called it an "excellent" meeting.

Privately, Nkomo officials say the situation between the two parties is "tense" and Nkomo "laid it on the line" that intimidation against his party workers had to stop.

Nkomo now seems to be in the driver's seat, forcing Mugabe to court him. Nkomo talked at a press conference about being "jilted" by Mugabe, who decided to run separately rather than within a unified Patriotic Front, a name Nkomo has now taken for his party alone.

This week, Nkomo, brought under the wing of his party 27 dissident former backers of Mugabe, some of whom actively plotted to kill the leader two years ago.

Nkomo has also been wooing the whites, calling for a spirit of reconciliation and reassuring them by telling blacks that under majority rule they will simply be able to seize land or jobs.

The guerrilla leader, formerly based in Zambia, even has taken the offensive on the Viscount issue, telling white businessmen, "that was an act of war. When we lost 317 schoolboys during a [Rhodesian] raid into Zambia, it was an act of war. The war is over."

For security reasons, Nkomo's first press conferences were held in the black townships surrounding Salisbury and always on short notice. This week he announced a press conference a day in advance and held it in a downtown hotel well known as a popular hangout for white Rhodesian troops and their friends.

In contrast, Mugabe, the target of two attacks, has shifted from meeting the press in the city to holding sessions, sometimes with only half an hour's notice, at his suburban home.

Mugabe lately seems to spend most of his time fighting with the British colonial administration of Lord Soames, the governor, who has boxed him into a corner on the issue of voter intimidation.

Mugabe has warned he may pull out of the election and go back to war if Soames carries out threats either to ban his party in some districts or disenfranchise large numbers of voters in its areas because of intimidation. Such a move could help Nkomo indirectly.

Many analysts, however, discount Mugabe's threats, since he is still expected to win the most seats and any return to the battlefield could result in a bloodbath.

Meanwhile, Muzorewa continues to flounder, running a "dreadful" campaign, as one informed foreign analyst put it simply attacking Mugabe and Nkomo more and more frantically. He may have more support in the countryside than sophisticated blacks in Salisbury think, however, and he could bounce back if Mugabe continues to have troubles. Both men are competing for the votes of their majority Shona tribesmen.Nkomo, from the minority Ndebel tribe, is gambling that tribalism is not as big an issue as conventional wisdom indicates.

Generally, Mugabe is expected to get between 30 and 35 seats, Nkomo between 20 and 25, Muzorewa about 20 or less, with the remainder going to minor parties but predictions vary widely. Horsetrading will doubtless start the minute the result is known March 2 or 3.

In such a situation, the British ability to wield influence is considerable, since Soames is merely called upon to select the person he thinks most capable of commanding a majority, not necessarily the leader in seats.

The "critical mass" for Mugabe is probably between 35 and 40 seats. If he achieves that, members of other parties would likely swing over to him to be with a winner, making an anti-Mugabe coalition impossible.

Anything less, however, could open the door for Nkomo if he finishes second. To place third would most likely leave him in a very junior alliance with Mugabe.

Publicly, the British hold to the line that they are neutral. But one official just smiled and failed to dissent when asked about the idea that Britain has shifted from being for Muzorewa, who has had white backing, to being simply anti-Mugabe.

There is little question that Soames and Nkomo, two jovial fat men with a love of the good life, have far more in common than has the governor with the rather ascetic Mugabe. At a party before the guerrilla leader's return from exile three weeks ago, Soames was reported to have remarked that Mugabe "sounds like a terrible fellow."

Soames' meeting this week with Nkomo and Mugabe were characterized by the British spokesman, as respectively, "warm and friendly" and "cool and correct."

Current slow repatriation of refugees is to Mugabe's disadvantage, since most are his supporters in Mozambique. He could lose upwards of 100,000 potential votes, about 3 percent of the eligible voters, if the trickle is not accelerated.

One British official did nothing to hide his glee at reports that the Mugabe dissedents had given him trouble at a press conference.

A source admitted that Mugabe was "the bogeyman" to Britian but added that one could hardly expect the British government of Conservative Prime Minister Margaret Thatcher to assist an avowed Markist candidate.

Smith recently signalled to his white Rhodesian followers that Muzorewa may not make it and they may have to switch to Nkomo to block Mugabe.