The protective cloak of John and Robert Kennedy on the presidential candidacy of Sen. Edward Kennedy was demonstrated in this central Texas hamlet by an auto parts salesman who bluntly said his support of the youngest Kennedy was a direct result of "the family bloodlines."

Our interviews with voters here suggested that family connection remains more important to Democratic voters than Kennedy's still-murky programs and policies or his troubles with Chappaquiddick. If so, Ted Kennedy still has the edge over Jimmy Carter for the nomination.

Thus, "family bloodlines" are the chief protection of Kennedy's otherwise vulnerable candidacy. They submerge his position on health care, deficit spending and many other issues that might sink any other candidate.

The 51-year-old auto parts salesman was one of 43 professed Democrats we interviewed in a weather-vane precinct in Pflugerville (population: 650), north of Austin, with a questionnaire prepared by Patrick Caddell's Cambridge Survey Research. Asked whether there was "something you particularly like" about Kennedy, he replied: "Yes, the family bloodlines."

He had voted for Carter in 1976, just like the young wife of an air conditioning engineer whose views of Kennedy were astringent. She told us: Kennedy has "misled" the American people by not telling the whole truth about Chappaquiddick; the phrase "big spender" applies more to Kennedy than Carter; the phrase "concerned about the average person" applies more to Carter than Kennedy. Yet she favors Teddy over Jimmy. Why? "I know the most about him because of his brothers."

Caddell selected Precinct 202 here as a barometer of Texas Democratic voting. Of the voters interviewed, Kennedy had 15; Carter, 12; and Gov. Edmund G. Brown Jr., 2 (with the balance undecided). For Carter, that was abysmal: one-third of 1976 pro-Carter voters we talked to have defected from the president.

Yet on the issues Carter towered over Kennedy. Take what for a decade has been Kennedy's overriding issue: national heath insurance. Only five voters preferred Kennedy's more costly, total health care coverage; 18 supported the presidents more modest and cheaper program.

Carter fared badly on his handling of inflation; 30 voters said they could not understand his program and only four called it "good." But Kennedy did even worse: 32 voters could not explain Kennedy's anti-inflation policies and only three thought they were any good.

Thus, the protective effect of family over substance showed through on the economic issue. Kennedy outscored Carter better than 5-to-1 as a perceived "big spender" in this rural conservative country. Kennedy also outpointed Carter on being "too liberal" and was in turn swamped by Carter (7-to-1) on the question of who came closer to being "a moral man."

As for Chappaquiddick, a surprising total of 23 voters -- many of them preferring Kennedy for president -- believe Kennedy "has misled" the American people and not "told the truth." A 25-year-old school administrator told us he believesKennedy has concealed what happened at Chappaquiddick, but still plans to vote for him. Asked for "something in particular" he likes about Ted Kennedy, he said it is time "for a person with strong ideas, and, like his brothers, he appears to be strong." That was true, he added, even though Kennedy has "a lot of scandal behind him."

The political problem for Kennedy is obvious: if Chappaquiddick should become acute later in his campaign as Carter's aides hope or if the "big spender" label begins to hurt in a country seeking balanced budgets and lower taxes, Kennedy may find that those "family bloodlines" might not bear the burden.

That possibility seemed to be inherent in answers to our questions about recent Kennedy television interviews. Slightly more than half said they had not seen any of them, but the impact on those who had was negative: by 2-to-1, they now take a "less favorable" view of the senator.

Therein lies the vulnerability of Kennedy's candidacy. Against widely unpopular positions and the burden of Chappaquiddick, he relies heavily on the memory of his martyred brothers. How long that will suffice in Pfulgerville and elsewhere remains to be seen.