text: SAN FRANCISCO, May 24— Mario Obledo frankly explains that he built his candidacy for the Democratic nomination for Governor of California on his Hispanic background.
  
  He sees the primary June 8 as a testing time for Mexican-Americans and the California Democratic Party as well as for his political aspirations.
  
  There are undertones of a sense of mission in the words used by Mr. Obledo, one of 12 children reared by illegal Mexican immigrants in a tiny house on an alley off a dirt street in San Antonio's barrio.
  
  ''I think that whatever I get will be a plus,'' he said. ''We started from zero. This is the first time we have had a person be a viable candidate for Governor in this state.''
  
  For seven years, until he resigned to run earlier this year, Mr. Obledo was Gov. Edmund G. Brown Jr.'s Secretary of Health and Welfare.
  
  Now 50 years old, Mr. Obledo worked as a licensed pharmacist while he studied law. He was a founder and chief counsel of the Mexican American Legal Defense and Education Fund, which has its headquarters here. He was a teaching fellow at Harvard Law School for eight months before joining Governor Brown's cabinet in 1975.
  
  ''We were on public relief,'' he said while discussing his childhood. His four brothers were convicted of such crimes as burglary, robbery and narcotics, but he was never jailed, he said, explaining: ''Every neighborhood had its own gang, if you want to call it that. I was involved in everything, I guess, that everyone else was. I just never happened to get caught in a serious situation that would embitter me to the point where I would continue in that pattern.'' Most Are Democrats
  
  About 4.5 million of the 22 million residents of this state are themselves immigrants or descended from immigrants from Mexico, Puerto Rico and Central and South America. Of the million of these who are registered to vote, most are Democrats. There are 5.6 million Democrats among the 10.7 million California voters. There are few prominent Hispanic politicians on the California scene; only six of the Legislature's 120 elected members are Hispanic.
  
  ''I figure 1.2 million votes will win the Democratic nomination,'' Mr. Obledo said in an interview. He brushed aside the California Poll of the first week of May, which showed him with just 3 per-cent of the Democratic vote, as against 75 percent for Mayor Tom Bradley of Los Angeles and 11 percent for State Senator John Garamendi of Stockton.
  
  ''I figure at least 70 percent of us will vote in the primary,'' he said. ''That would be 700,000, and I expect to get better than 70 percent of that. So you see that gives me 500,000 votes going in.
  
  ''I think I can get the balance from a cross section of the voters of this state. After all, I served as secretary for seven years. My name is known amongst a lot of provider groups, recipient groups, and grantees of Government programs. I must have addressed 1,000 meetings.''
  
  He said he had had no organizational support from ''Anglos,'' meaning whites, but said, ''I think I have a lot of Anglo friends and sympathizers who will vote for me.'' Help From the Farm Workers
  
  His strongest volunteer forces have come from among Hispanic Americans. The United Farm Workers Union, led by Cesar Chavez, which has largely Hispanic members, has given him his largest campaign donation, $50,000, and has promised to provide precinct workers in the last week before the June 8 primary election, he said. He expects to spend $300,000 by the election.
  
  The Obledo candidacy, with its strong ethnic tone, comes in a year when the traditional Democratic party institutions, such as labor unions and party workers, back Mayor Bradley, who is the first black candidate with a chance to win the gubernatorial nomination.
  
  ''I think it's time the Democrats supported someone from our constituency,'' Mr. Obledo said in the interview, held in his campaign headquarters on Olympic Boulevard in downtown Los Angeles. He said a disastrous defeat for him might turn Hispanic voters away from the polls in November to the disadvantage of the Democratic nominees.
  
  Asked if he would support Mayor Bradley if the Mayor won the primary, Mr. Obledo said: ''It's too early to tell. First I have to know what he stands for and I can't find that out.'' Mr. Obledo described the Mayor's refusal to meet him in debate as ''a sad commentary.'' Would Close Nuclear Plants
  
  Mr. Obledo's campaign issues tend toward the traditional liberal Democratic positions of help for education, for the poor and for the disadvantaged. He favors a nuclear weapons freeze, and of nuclear power plants he says, ''I think we ought to close them up.''
  
  In the interview, he described himself as firmly opposed to construction of the Peripheral Canal, which would increase the amount of water exported from Northern California to Southern California. Earlier, he had tentatively supported a ballot measure that would accomplish that, but now says his further studies persuaded him it was too costly.
  
  One position he takes would probably make him unique among governors: He has supported Argentina on the Falkland Islands. ''The security and well-being of our country rests on the relationship we develop with the nations in our hemisphere,'' he said, adding that England was ''declining as a prestigious power.''
summary: Mario Obledo frankly explains that he built his candidacy for the Democratic nomination for Governor of California on his Hispanic background.   He sees the primary June 8 as a testing time for Mexican-Americans and the California Democratic Party as well as for his political aspirations.   There are undertones of a sense of mission in the words used by Mr. Obledo, one of 12 children reared by illegal Mexican immigrants in a tiny house on an alley off a dirt street in San Antonio's barrio.   ''I think that whatever I get will be a plus,'' he said. ''We started from zero. This is the first time we have had a person be a viable candidate for Governor in this state.''