Los Angeles Mayor Tom Bradley has consistently enjoyed the most favorable image rating in the opinion polls of any politician in the state.

The polls also showed, even before Bradley won the Democratic gubernatorial nomination in last June's primary, that he would defeat any of his potential Republican rivals easily.

Now, however, many political professionals perceive that Bradley has a tough fight on his hands and they predict that, at best, he will win by a narrow margin on Nov. 2. Despite protestations from many Californians that the race issue is behind them, political observers suspect that one reason is that Bradley is black.

In an August, 1981, Mervin Field California Poll, Bradley got 55 percent support, a 24-point lead over his Republican opponent, state Attorney General George Deukmejian.

But Field exit polls on the June 8 primary day showed Bradley's lead dwindling to a slim 3 percentage points. Bradley's campaign managers attributed this to the publicity Deukmejian received in his tough battle with Republican Lt. Gov. Mike Curb, who was named finance chairman for the Republican National Committee today. Now the campaign managers cite polls showing Bradley leading Deukmejian by 8 points.

Nelson Rising, Bradley's campaign chairman, told reporters at a recent breakfast meeting that "race will not figure into the final equation of this campaign. Tom Bradley is extraordinarily well known throughout the state. People know him and are comfortable with him."

Rising said the Bradley campaign has poll data, which he refused to release, that support his contention. He added that neither Bradley nor his managers will discuss the possible effect of race on the November election because "you don't go back and re-litigate what you have decided is not an issue."

But Field said that as he traveled around the state this summer, one of the first questions he was asked by Republicans and Democrats was how Bradley's race will affect the election.

"It's uppermost in their minds," Field said. "And the fact that so many people talk about it, I think that anybody who says there is no residual resentment toward a minority group member running for public office is a fool. It exists."

State Sen. Alan Sieroty, a liberal who represents west Los Angeles, predicts that the election will be close.

"I think," Sieroty said, "that Bradley is still ahead, but you don't know how much latent racial bias there may be that is not disclosed in the polls."

Field agreed that prejudice tends not to be revealed in poll data.

"In respect to whether Bradley's blackness will deter voters, we will not get complete candidness. It prejudice is something that's tough to explore. It's tough to intellectualize. It's a rumbling in somebody's psyche. There is no question that race will be a factor. The question is how big a factor."

Political consultant Joe Cerrell, responding to Rising's contention that race would not be an issue, said, "I don't believe it . . . . I think it's wishful thinking on their part."

In 1974, Cerrell managed Mervyn Dymally's successful campaign for lieutenant governor. Dymally, now a congressman, is black, and Cerrell said that, during the campaign, "We hid him."

Cerrell said a candidate for statewide office can be "hidden" by avoiding television appearances. "NBC would call and want Merv for an interview show . We'd say, 'Sorry, he's going to be in Stockton that day,' or, 'Sorry, we'll be in Redding.' We turned them down so often we had an open invitation for an appearance."

In 1966, Yvonne Brathwaite Burke was the first black woman elected to the California Legislature. In 1972, she was the first black woman elected to Congress from California.

In 1978, Burke was defeated by Deukmejian in a race for state attorney general and in 1980 she was defeated for the Los Angeles County Board of Supervisors.

Burke said she is not convinced that Bradley has that tough a campaign, but asked about race as an issue, she said, "I think it's there."

Burke's opponent in the 1980 county supervisor campaign used school busing as a central campaign theme. Burke also had repeatedly opposed busing, which, in any case, is not in the jurisdiction of a county supervisor.

Shortly after the election, Burke said she believed her opponent "was able to say, 'Well, she really does believe in busing. And it was believable to people because . . . I was black. And then, toward the end, when he had not been able to pull up in the polls , he sent my picture throughout the district."

Just as Burke believes that her opponent used busing as a euphemism for race, some Californians believe that if there is a racial euphemism in the Bradley-Deukmejian race, it would be crime, an issue of deep concern for most Californians.

Bradley was a policeman for many years, which helps protect him from charges he is soft on crime. But he opposed, on constitutional grounds, Proposition 8, the "victim's bill of rights" passed overwhelmingly by voters last June.

While Bradley said he supported the measure's victim-assistance elements, he opposed the proposition as unconstitutional, and said it would create chaos in the courts.

Deukmejian made his support of Proposition 8 one of his major campaign themes. And many expect that the state Supreme Court, already criticized in quarters as favoring the rights of defendants over victims, will declare the measure unconstitutional before the Nov. 2 general election. That would be greeted by a lot of resentment.