By all objective standards, Sen. Charles McC. Mathias Jr. should have little to worry about this election year. He has only token opposition in the May 13 Republican primary in Maryland and is heavily favored to win a third term in the fall over his Democratic opponent.

So why is Mathias getting up before dawn to make breakfast speeches to business executives, attending weekend cookouts with labor unions and spending a Saturday night, as he did recently, courting a dozen folks in a small restaurant in his hometown of Frederick?

Asked that question as he munched on a scalding hot meatball in the dimly lit dining room of Erni's Italian Kitchen in Frederick, Mathias invoked the words of Jesse Unruh, the long-time power broker of California Democratic politics: "Money is the mother's milk of poilitics."

Thus, despite the lighweight opposition, the 57-year-old Mathias is spending much of his time trying to finance a primary and general election campaign that will cost $750,000, maybe even $1 million. As of a few days ago, he had raised $262,000 and spent $193,000. He hasn't even begun a media campaign, and television chews up money as fast as it does situation comedy pilots.

The agony and ignominy of raising money is "uncomfortable and embarrassing" to the urbane, low-keyed Mathias, who unsuccessfully supported legislation that would have provided public financing of congressional campaigns.

"It distracts candidates' time from more substantive issues," Mathias said, "but that's the way it is. It has to come from somewhere."

Among the places it comes from are intimate little gatherings such as the one in that Frederick restaurant, to which tickets were sold at $25 each. The food and drinks cost Marylanders for Mathias -- the name of his official fund-raising committee -- $287.50. Only because one longtime family friend paid $300 for his ticket, and several others gave $100 each, did the affair show a net profit, unless you count the candidate's time and lost opportunities elsewhere.

The slim turnout was blamed on the failure of the advance man to take into consideration a competing event -- the annual father-son banquet of the Frederick Touchdown Club -- which Mathias attended later in the evening.

On the campaign trail, a candidate takes money where he can find it, big or small, near or far.

Early this year, for instance, Mathias made a West Coast swing that included wooing fat-cat Republicans at a private dinner in San Francisco and two events in Los Angeles on Super Bowl weekend. At Los Angeles he appeared at a cocktail party at the Beverly Wilshire Hotel put on by the National Republican Senatorial Campaign Committee, at which 100 people paid $500 to mingle with Mathias and two other senators and to sit together the next day at the Super Bowl game.

Later this year, Mathias will make hs traditional fund-raising trip to New York, where he will meet with Wall Street financiers and Manhattan bankers.

Most of the time, however, the fundraising is glamorless and, as Mathias says, embarrassing. Precious hours that might be spend wrestling with the latest internaitonal or domestic crises are consumed telephoning potential contributors or writing thank-you notes to those who already have come across.

Mathias recalled that the late Hubert H. Humphrey talked about the "standing in the front room pumping hands, pretending you don't know what's going on in the back room" where the campaign's finance chairman is making the hard sell to the guests.

But most of the money comes as the result of direct efforts of the candidate. "Friends can do some of it for you," Mathias said, "but realistically, you've got to do most of it yourself."

And there is virtually no one who Mathias -- universally viewed as a Mr. Clean of the Senate -- won't take money from. "It's the safest approach," he said. "We throw out a wide net to attract the interest of as wide a range as possible. If you do business with the widest possible spectrum, the more impersonal it is the less likely you are to create the entanglement we want to avoid."

So the invitations go out from Mathias' campaign headquarters in suburban

Two big public events netted the Mathias campaign $160,000.

About $100,000 came from a $100-per-person "Salute to Ann and Mac Mathias" on Feb. 18 at the new Baltimore convention center. It was, as Mathias' press aide Jack Eddinger described it, "your standard, garden variety Maryland fund-raiser," with potted palms, banners and balloons carrying out the black-and-orange color scheme borrowed from the state flag, and tables of food and liquor scattered around the hall.The crowd of 1,000 included a heavy sprinkling of labor union leaders, who traditionally have forsaken the Democratic party to support Mathias.

The other event was a reception for political action committees (PACs) at the Capitol Hill Club last Oct. 8. The formal invitation said "the pleasure of your company" is requested at a reception in honor of Sen. Charles McC. Mathias, but the black-and-white card more accurately could have substituted the words corporation, labor union, trade associaiton or other special interest group for the word "company."

Enclosed with the invitations, which were sent to 1,000 PACs that had been selected by a committee of 20 Mathias supporters, were cards offering the recipients a choice of contributions: $250, $500 or $1,000.

The mailing produced about $60,000. The receptions are formalities -- three or four a week are held in the Republican Club near the Capitol -- so many PACs simply mailed their contributions to Mathias' storefront headquarters in Towson. About 200 lobbyists, however, attended that Mathias event in the club's Eisenhower Room, so they could rub shoulders with the Marylander and his Senate and House colleagues who take turns showing up for each other's fund-raisers. For Mathias, the honorary hosts were Sens. Howard H. Baker Jr. of Tennessee, Ted Stevens of Alaska, John Tower of Texas and John Heinz of Pennsylvanis (who goes to many receptions as chairman of the GOP's senatorial campain committee); and House Minority Leader John J. Rhodes of Arizona.

Some of the PACs didn't wait for the invitation. The Air Line Pilots Association and the United Steelworkers Union, for example, each mailed checks for $2,500 last June.

Mathias doesn't keep a running count of where his money is coming from, but in preparing for a recent primary debate, he said, he "went back over the contributions and was comforted to find that labor and management support was of the same magnitude."

According to the latest financial statement filed with the Federal Election Commission, as of April 15 Mathias had received $52,450 from labor unions and $36,350 from business, trade association and professional groups. Fifty-two unions gave Mathias $1,000 or more, with the Steelworkers and United Auto Workers contributing the maximum $5,000 permitted by FEC regulations.

Six years ago, when Mathias last faced the voters, he imposed a $100 limit on contributions, even though the law didn't require it.

About 9,000 persons and groups contributed $450,000 to Mathias' 1974 campaign, or an average of $50 per gift.

Mathias scrapped the $100 limit for the 1980 campaign, citing inflation and new federal regulations that, while falling short of his goal of public financing, set strict guidelines for contributions. The maximums are $1,000 for individuals and $5,000 for PACS.

The big push these days is to tap individuals. Dr. Milton S. Eisenhower, former president of Johns Hopkins University and honorary campaign chairman, and Baltimore banker H. Furlong Baldwin, the finance chairman, have written to business and civic leaders throughout Maryland in an effort to raise another $75,000 before the primary.

Not all his Republican colleagues in Congress agree with Mathias' fund-raising philosophy.

Sen. Orrin Hatch (R-Utah) picks and chooses the PACs from which he seeks money. If he doesn't agree with their view, Hatch said he doesn't want their money. For example, he said he would not take contributions from a pro-abortion group or from Ralph Nader, adding, "but of course, they wouldn't offer, either."

Rep. Millicent Fenwick (R.-N.J.) thinks Mathias is "the closest thing to a saint there is in politics," but she refuses to accept any PAC money, calling them "the greatest evil that is still lawfful." Fenwick, who shares Mathias' view that congressional campaigns should be financed by $1 checkoffs on income tax returns, as are the presidential races, said PACs "usually pay [contribute] according to your voting record."

Fenwick said it is "a myth that tremendous sums are needed" for political campaigns. Her own rule is that she will spend as much of her own fortune as her opponent collects from PACs a choice she concedes is not available to less wealthy candidates.

Mathias' campaign manager, John Bamacus, who is on leave from Frostburg State College where he teaches political science, agrees with Mathias that fund-raising is the least rewarding aspect of campaigns. But Bambacus adds, "it's necessary. It's also positive and healthy to give to a cause in which you believe. It's a way people can participate in a campaign." c

Not only does raising money require a lot of a candidate's time, but so does acknowledging the contributions, which is a key to getting money the next time. a

As he sat in his Capitol Hill office late one evening, signing thank-you notes to contributors, a contemplative Mathias philosophized about fund-raising.

"We wouldn't have financial problems if political education were as Garfield described the best university: 'Mark Hopkins sitting on one end of a long and a student on the other end.' But in modern society, fund-raising can't be avoided. It becomes a major part of your effort, and it gets in the way of what we'd like to do in a campaign."

Mathias was asked why he thought people give money to political candidates.

"What's the 'quid pro quo'?" he pondered. "A good question. Why do people do it?"

The reason why one PAC contributed to Mathias will be the topic of another story.