Democrat Michael Dukakis spent the morning in the hospital as his wife, Kitty, underwent delicate spinal surgery. Vice President George Bush arrived back in Washington from his summer home and immediately went to visit cancer-stricken Salvadoran President Jose Napoleon Duarte at an area hospital. The surgery on Mrs. Dukakis was begun early today and completed in the afternoon. ``Preliminary indications look good,'' said Martin Bander, a spokesman for Massachusetts General Hospital in Boston. Bush was to welcome President Reagan back from his Moscow summit trip late today. Before taking a helicopter to Walter Reed Army Medical Center, Bush said of Duarte, ``I plan to wish him well and share our country's appreciation for all he's done for democracy.'' Bush, returning to Washington today after a week of strategy talks at his summer home, said he was convinced his campaign is ``on the right track'' despite a rash of recent surveys suggesting he trails Dukakis, the Democratic front-runner. ``I'm not going to be stampeded by polls that don't mean anything,'' the vice president told reporters on Thursday, as he was preparing to leave his oceanside retreat at Kennebunkport, Maine. Meanwhile, a poll in California gave Dukakis a substantial lead over Jackson, his only remaining rival, in Tuesday's primary. But it suggested Jackson, who has campaigned heavily in the state, was gaining ground. Dukakis cut short a California campaign swing on Thursday after his wife's doctors decided to perform ``urgent'' surgery on herniated discs pressing dangerously on Mrs. Dukakis' spinal cord. Dukakis, who was spending the night at the hospital, visited his wife late Thursday night and told reporters afterward: ``She's in good spirits, looks good and is anxious to get this over with.'' The governor said he hoped to resume campaigning this weekend if the surgery went well. Jackson was campaigning today in New Mexico and Montana, whose primaries on Tuesday have been largely overshadowed by big same-day contests in New Jersey and California. The four races, with a total of 466 delegates at stake, close out the Democratic primary season, and offer Dukakis a chance to clinch the nomiantion. Of the 2,081 delegates needed to nominate, the Massachusetts governor has nearly 1,800. Jackson trails with fewer than 1,000. In California, a poll conducted for the San Francisco Examiner and San Francisco television station KRON indicated Dukakis led Jackson by 24 percentage points, 52 percent to 28 percent. In a similar survey two weeks ago, he led by 37 points. The poll, for which 600 registered Democratic voters were questioned on Tuesday and Wednesday, has a margin of error of 4 percentage points, the Examiner said in Thursday's editions. Jackson was expressing hopes that a debate with Dukakis could be arranged before Tuesday's primary. The two Democrats had been scheduled to debate Thursday afternoon in California, but Dukakis canceled out after his wife's doctors said they wanted to operate without delay. ``My impression is that when you have anything that involves the spinal cord, the faster you move on it the better,'' Dukakis said as he was flying home Thursday night. Bush, meanwhile, was returning to Washington today in time to greet President Reagan, who will be back from tonight from the superpower summit. Some Bush supporters, eyeing a series of public-opinion surveys last month that gave Dukakis double-digit leads, have been urging Bush to try to set himself apart from Reagan on a few issues. Bush has edged away from the president on a matters such as Panama's Gen. Manuel Antonio Noriega, under indictment on drug charges, and Attorney General Edwin Meese III, under investigation by an independent counsel. But he has refrained from any dramatic breaks with the president. ``We've got a game plan. We've staying with it,'' he said. ``You're not going to see any drastic change in campaign plans.'' On Thursday, he was asked about Reagan's suggestion that Soviet reluctance to issue exit visas stems from bureaucratic problems rather than Kremlin policy. Bush sidestepped the question. But he went on to criticize Soviet human rights policy in stronger terms than the president has used. ``I think we have very different views on human rights than the Soviet Union,'' he said. ``I would suggest that Soviet retaliation against us, saying we've got human rights problems, is mixing apples and oranges.'' The vice president added: ``We've got some problems, but they're not problems of human rights.'' Still, he hailed Reagan for raising human rights issues, saying: ``I think the Soviet Union should adhere to these high standards the president is talking about.'' Dukakis, too, made a point of praising Reagan for bringing up human rights during the summit trip. ``We take pride in the message of freedom and human rights that President Reagan brought with him to Moscow,'' the Democratic candidate said in a statement issued by his campaign.