Western Air Lines flight 501 touched down at Los Angeles International Airport on a sunny day last week, bringing Lawrence J. Hogan 3,000 miles from his Prince George's County home to a reception of wealthy southern California conservatives.

They had gathered in an opulent 17th-floor suite on Wilshire Boulevard to hear Hogan, the leading Republican candidate for the U.S. Senate seat from Maryland held by liberal Democrat Paul S. Sarbanes, make his pitch.

Standing in the oak-paneled library of the exclusive Regency Club, surrounded by fine porcelain, rare tapestries and vases of fresh flowers, and looking out over the sprawl and haze of west Los Angeles, Hogan repeated the message he delivered earlier that day to officials at the California headquarters of Getty Oil and Dart Industries: "Larry Hogan can beat Paul Sarbanes," Hogan emphasized. "But only if you help. I can't do it without your help. I can't do it without your money."

Hogan, the 53-year-old Prince George's county executive and former three-term congressman, is seeking financial support, as well as national attention for his Senate race, from conservative political action committees around the country. With the aid of the national Republican senatorial campaign committee, whose officials say Sarbanes is the most vulnerable incumbent in the Senate, Hogan is shifting from a strategy that until recently had produced mostly small contributions from inside Maryland -- and little recognition outside.

After a slow campaign start, which was marred by political infighting in the Maryland GOP and an ineffective campaign organization, Hogan and national party officials have combined forces to close state Republican ranks behind him, improve his campaign staff and focus on Sarbanes.

Now the Republican candidate is soliciting contributions in the country's wealthiest bastions of conservatism -- Texas and southern California, among others -- while appealing for electoral support from Maryland's overwhelming majority of middle-class and blue-collar Democratic voters.

"Money is everything," Hogan said as he drove a rented white Oldsmobile along palm-tree-lined Santa Monica Boulevard, between stops with business officials in Los Angeles and conservative Orange County. "All these PAC people talk to each other. Now the word is spreading through the community that I'm turning the race around. These PACs are interested because they want Sarbanes out."

After two days of meetings with conservative California business leaders, and two hours of sipping cocktails and nibbling on fancy hors d'oeuvres at the Regency Club -- where Hogan, at ease in the posh California environment, shook hands, spoke briefly, answered questions and distributed a glossy PAC kit that compared his pro-business record with Sarbanes' votes in the Senate -- the Republican candidate had garnered at least four campaign pledges.

Citizens for the Republic, the offspring of President Reagan's personal fund-raising committee, sponsored the reception, and invited Hogan and three other conservative Senate candidates, Rep. Robin Beard of Tennessee, Gene Knorr, a North Dakota consultant and former Treasury Department legislative aide, and Jim Keck of Nebraska, former vice commander of the Strategic Air Command in Omaha, to attend it. Citizens for the Republic has given Hogan $5,000 and plans to give more after the primary.

Louis Barnett, the Citizens' committee's political director who conceived last week's event, said Hogan's performance was "phenomenal."

"Frankly, on the basis of seeing him and hearing him, I think the guy is a little powerhouse," Barnett said. "I wish we had gotten involved earlier. I'm really very excited about him. He scored the most points with me at that gathering. I think he can go all the way."

Barnett said he expected Hogan to receive contributions, probably in the $250 to $750 range, from most of the approximately 30 PACs at the reception, which represented a collection of southern California's aerospace, energy, utility and Fortune 500 companies.

Earlier this summer, after potential GOP primary challengers withdrew, Hogan made a one-day trip to Dallas, appearing at a gathering of several dozen Texas corporate contributors. He received a contribution of $5,000 from Dalenpac, a Dallas-based energy group; $2,500 from the Hunt Committee for Sound Government; $1,000 from the Houston Political Action Committee, and a pledge for an undisclosed amount from the political action committee of Southland Corp., which owns 7-Eleven food stores.

Other conservative groups have also contributed: $2,500 from the Denver-based PAC of beer magnate Joseph Coors, President Reagan's New Right political ally, and $4,000 from the right-wing Committee for the Survival of a Free Congress. Hogan's campaign staff also is planning fund-raisers or receptions in Denver and Connecticut.

But even with growing Republican interest in his campaign and the recent PAC contributions, Hogan has raised only about $300,000 with less than two months left before the Nov. 2 general election. Sarbanes, by contrast, has a war chest totalling $950,000, much of it from labor organizations outside the state.

Hogan is counting on gaining momentum from $230,000 the national party will make on his behalf after the Sept. 14 GOP primary, in which he is a strong favorite to defeat two opponents, William A. Albaugh and Donovan B. Finch, and on what he terms the "grapevine" effect of PAC attention.

During his blitz of southern California, Hogan and his campaign finance director, Zorine Shirley, met privately for about 45 minutes with PAC officials from six companies: Getty, Dart, TICOR, a subsidiary of Southern Pacific Railroad; Whitaker Corp., a yacht-builder, chemical producer and hospital care group that has several subsidiaries in Maryland, including one in Bethesda; Karcher Enterprises, which owns the Carl Jr's restaurant chain in California, Nevada and Arizona, and Fluor Industries, an energy group with oil, gas and coal concerns.

Three months before Hogan's tour, when the Maryland GOP still was squabbling over internal differences, officials from the national party's senatorial committee came to California and made some of the same corporate stops as Hogan, paving the way for him by spreading the word to conservative contributors that they think Sarbanes is vulnerable and that a pro-business Republican might be able to win his seat.

"They said this was their No. 1 priority," said Dart-Kraft PAC treasurer Kristi Gillet, who met with the national officials during the summer and then with Hogan last week. "They are the most optimistic about the vulnerability of Paul Sarbanes. We'd like to share their enthusiasm. We might not be quite as optimistic. But we looked at Larry's record in Congress and as county executive, and he has been able to demonstrate that he is a viable candidate. Now his campaign is moving out of the idealistic category, into the realistic, do-able, winnable category."

The original Dart political action committee, created in 1976 by long-time Reagan friend and Los Angeles businessman Justin Dart, contributed $245,000 to candidates in the 1980 election who were "business-oriented, fiscally responsible and who believe in less government and less taxes," Gillet said.

In many ways the Dart PAC represents what Hogan sees as the ideal contributor to his campaign: It is associated closely with Reagan and his philosophies, which Hogan firmly supports, and it has been involved in political elections for several years. Also, Hogan hopes that Dart's interest might generate broader attention among similar PACs because of Justin Dart's personal participation in and influence on the early "PAC movement."

Dart officials originally became interested in the Maryland Senate race when they realized that Sarbanes was up for re-election. Most of their information about Hogan has come from pro-business groups, such as the U.S. Chamber of Commerce and the National Association of Manufacturers, various conservative publications and the Republican senatorial campaign committee. The personal meeting with Hogan last week, Gillet said, also helped persuade them of the importance of his campaign.

But even though Hogan fits Dart's specifications for support, its contributions may be limited. Several days after Hogan's visit Gillet and two other PAC officials sent a $1,000 check to Maryland, one-fifth the maximum allowable contribution under federal law.

"Unfortunately we don't have an overabundance of funds," Gillet said, explaining that the large, successful Dart PAC had to be reorganized last year after Dart Industries merged with Kraft Foods. "We found ourselves in quite a bind."

The new Dart-Kraft PAC had less than three months to raise funds for the 1982 elections, Gillet said, and has to divide $72,000 among 13 Senate candidates and 63 campaigns for the House. Dart-Kraft will contribute $1,000 to Virginia's GOP Senate nominee, Rep. Paul S. Trible.

Large contributions from other PACs may be an equally elusive goal for Hogan. "I don't want to encourage him when we are considering his race among so many," said Tom Spencer, PAC director for Getty Oil, which will give $60,000 in total political contributions this year. "From what I heard and read, he seems to be free-enterprise oriented and we're looking for a pro-business candidate. Generally my impression of Larry Hogan was good. But we haven't made a final decision."

Spencer said the Getty PAC usually makes a maximum contribution of $1,000 for Senate races and like many cautious business PACs, almost always waits until after primary elections and the adjournment of Congress before sending checks.

"It's a fallacy to think that all these PACs are going to send a $5,000 check," said Barnett of Citizens for the Republic, explaining that PACs raise money partly through direct mail and individual solicitations. "Those of us who can give $5,000 are few and far between."

Hogan, meanwhile, is banking on the business community's interest in unseating Sarbanes, and added information about his own candidacy, to generate money and momentum for his campaign in the next 60 days.

"In spite of the odds," Hogan stressed repeatedly during his meetings with business leaders, "the Democrats have learned not to bet against Larry Hogan. And it's not in your self-interest to bet against me now. I'm the only chance you have to replace Paul Sarbanes. You can't afford not to get involved in this race."