HOUSTON, JULY 1 -- Seven Democratic presidential hopefuls gathered here today for their first nationally televised debate, but before they made it onto the air at 9 p.m. (EST) the event was overshadowed by political repercussions from President Reagan's nomination of Judge Robert H. Bork to the Supreme Court.

The candidates, pressed for comment by the scores of journalists who also assembled here, expressed skepticism bordering on hostility toward the nomination, suggesting that the Senate confirmation battle could become heavily enmeshed in 1988 presidential politics.

One of the candidates, Sen. Joseph R. Biden Jr. (D-Del.), who chairs the Senate Judiciary Committee, said that although he would not reach a final judgment until he conducts a "full, fair and thorough hearing," he already harbors "serious doubts" about Bork.

"He appears to be settled in all his views; he appears to be someone who has a very sharp edge as to where he would see the court move," said Biden, adding that it would have been better if Reagan had nominated someone in the "mold of {retiring} Justice {Lewis F.} Powell" who has an "open mind" and would preserve the current balance and ideological diversity on the court.

Another Judiciary Committee member seeking his party's 1988 nomination, Sen. Paul Simon (D-Ill.), said he, too, was "going to reserve judgment." He, too, expressed misgivings: "You should not have people {on the court} who are rigid ideologues of the right or left . . . . The court should not be a pendulum that swings back and forth depending on the ideology of the president."

Former Arizona governor Bruce Babbitt said through a spokesman, "I learned all I need to know about Mr. Bork's character when he served as the executioner for the 'Saturday Night Massacre' of Watergate."

Rep. Richard A. Gephardt (D-Mo.) said Bork's role in that 1973 episode -- when as U.S. solicitor general Bork fired Watergate special prosecutor Archibald Cox after Attorney General Elliot L. Richardson and Deputy Attorney General William D. Ruckleshaus resigned rather than carry out President Richard M. Nixon's order to fire Cox -- weighed heavily against him. "The man who enabled Richard Nixon to fire Archibald Cox cannot be permitted to serve on the Supreme Court," he said. Gephardt also said he was disturbed that the nomination "seems to be the culmination of the Reagan administration's unworthy policy of applying ideological litmus tests to judicial nominees."

Massachusetts Gov. Michael S. Dukakis, without indicating whether he thought Bork should be confirmed, said through a spokesman that "I am very troubled by his role in the Saturday Night Massacre."

Sen. Albert Gore Jr. (D-Tenn.) said he would "follow the proceedings carefully and make up my mind accordingly . . . . I don't think it's a good nomination, but I'd like to see the hearings and read the record before deciding how to vote."

The seventh Democratic hopeful, Jesse L. Jacskon, could not be reached for comment before the debate.

The two-hour, seven-way debate, broadcast on the Public Broadcasting Service and jointly moderated by conservative commentator William F. Buckley and former Democratic National Committee chairman Robert S. Strauss, offered an early chance for a field of relatively obscure Democrats to audition before a national audience. Aside from Jackson, who ran in 1984, none of the seven is well known beyond the borders of his home state, and all were looking forward to tonight's encounter as the start of a televised march out of obscurity.

Still, given the season, the timing and the forum -- a midsummer's evening seven months before the first votes are casts in Iowa precincts -- few of the participants believed that a great deal was at stake. Many saw it more as a scouting session for future encounters.

"This is not exactly high noon in the streets of America," quipped Babbitt, who prepped for the event by speaking at a small fund-raising session with lawyers. He confided that he had never been able to watch a group presidential debate all the way through, and wondered how many voters would. PBS officials projected the viewing audience at 6 million to 9 million.

No debate is complete without some preliminary controversy over format and cast.

Earlier this week, Rep. Pat Schroeder (D-Colo.), who is considering a run for the Democratic presidential nomination, said she was disappointed that she was not included. Strauss said he understood that Schroeder did not make the sponsors aware of her interest until last Friday, and that by then it was too late.