PALO ALTO, Calif. — A former California governor’s endorsement of Mayor Giuliani could boost his strategy to use the Golden State as a bulwark in his campaign for the Republican presidential nomination.

The nod from Pete Wilson, who was elected twice as governor and twice to the Senate, underscores Mr. Giuliani’s appeal to California voters who are fiscally conservative but more liberal on social issues.

“Rudy’s executive experience and record of results in New York are unmatched,” Mr. Wilson said in a statement released by Mr. Giuliani’s campaign following an event the two men attended in Santa Monica, Calif. “Rudy has proven he is the leader and the problem solver this country needs as President, and he is the Republicans’ best opportunity to win the general election because of that.” Mr. Giuliani used the appearance to jab at the Democratic front-runner, Senator Clinton, over statements on Iraq and Iran that she made at a debate Wednesday night.

“We’re now on the sixth position and counting,” the former mayor said of Mrs. Clinton’s views on the American troop presence in Iraq, according to KNX-AM. “The sixth position is that she’s not sure if she can withdraw the troops by 2013.” Mr. Giuliani also faulted Mrs. Clinton for refusing to “make a commitment that we would stop Iran from becoming a nuclear power,” the Los Angeles Times reported on its Web site.

Mr. Wilson is well-respected in Republican circles and still has ties to the state party’s machinery. However, he carries the baggage of his role in promoting a 1994 ballot measure, known as Proposition 187, that some contend crippled the GOP in California by alienating the state’s fast-growing Hispanic population.

Messrs. Giuliani and Wilson differed over the measure, with the mayor of immigrant-rich New York denouncing the plan as “inhumane” and “mindless.”

“All that said, I’d rather have the endorsement of Pete Wilson than not have it,” a consultant to Republican political candidates in California, Arnold Steinberg, said. “He did win several statewide races here.” In 1996, Mr. Wilson made a run for the White House but quit early in the process.

According to recent polls, Mr. Giuliani holds a substantial lead among California GOP voters. A Field Poll taken last month showed the former New York mayor with 35% support, a former Massachusetts governor, Mitt Romney, with 14%, and a former senator from Tennessee, Fred Thompson, with 13%. Among those closely following the race, Messrs. Thompson and Romney did somewhat better but still trailed Mr. Giuliani.

If Mr. Giuliani does poorly in the earliest primaries and caucuses such as Iowa and South Carolina, which is possible due to the conservative bent of Republican voters there, he could reinvigorate his campaign with wins on February 5 in California and New York, the biggest of about 20 states holding primaries that day.

Political analysts call it a “firewall” strategy. However, the Iowa caucus is likely to take place on January 5, leaving candidates who do well in the early states a full month to boast about their successes and forcing those who do poorly to endure several weeks of questions about whether their campaigns are cratering.

“The real question is whether there will be a sort of media momentum effect, which could cause a jump [for some candidate] in California,” Mr. Steinberg said.

Mr. Giuliani’s strongest challenger in California could be Mr. Thompson, who appeals both to moderate and conservative voters. “Thompson has created quite a buzz out here,” an adviser to the former senator, Kenneth Khachigian, said. “He’s not seen as purely ideologically driven.”

Mr. Khachigian said Mr. Thompson will start stumping for votes in California next month. “There’s no question he’s going to be starting to spend more time here.”

Mr. Giuliani’s trip to California is built around a series of fund-raisers in the Los Angeles area yesterday and in Napa Valley on Friday. All the major candidates are involved in a fund-raising blitz ahead of a reporting deadline Sunday, at the close of the third quarter.