Had Sen. Charles McC. Mathias Jr. enjoyed six years ago the kind of overwhelming affection and loyalty showered upon him at a tribute here tonight, he might well have finished out his distinguished political career as the chairman of a major Senate committee.

But if any such thoughts crossed Mathias' mind, he kept them to himself tonight as he was feted by 1,200 people, including some of Maryland's and the nation's most distinguished citizens, at a retirement party at the Baltimore Convention Center.

"It's sort of an overwhelming experience," Mathias said as the powerful and famous and humble convened for what was billed as a "celebration of statesmanship," a dinner honoring the senior member of the state's congressional delegation who is retiring from politics this year.

Facing retirement from the Senate after 18 years, Mathias was honored by dozens of his colleagues, titans of industry, labor leaders who supported him despite his Republican affiliation, civil rights leaders, diplomats and most of the Democratic and Republican hopefuls who seek to replace him on Capitol Hill.

All paid $150 a head to pay tribute to a man who was sometimes an outcast in his own party, but who was described by Democratic Gov. Harry Hughes as a man who throughout his career "stood for principle over politics."

The proceeds from the dinner will go to the Johns Hopkins University School of Advanced International Studies, which will establish a program of foreign studies in Mathias' name. Mathias himself will begin teaching at Hopkins this winter.

"I don't anticipate it will be a sharp break," said Mathias of his impending semiretirement at the age of 64. "I will continue to take an active interest in public affairs."

No matter what he does, it is doubtful Mathias will ever have a more distinguished or admiring audience for his labors than the one that gathered here tonight.

From David Rockefeller to the head of the Maryland Watermen's Association, they came to honor Mathias for his work in civil rights, for peace and on behalf of the environment.

Maryland Comptroller Louis L. Goldstein, a Democrat, described him as a "Jeffersonian Republican," a seeming contradiction that nonetheless was as apt a label as any.

A Republican who prospered in an overwhelmingly Democratic state, Mathias enjoyed an appeal that transcended party label and ideology. Though his retirement leaves Maryland Republicans without a senior statesman to carry their standard, it seemed there were as many Democrats here tonight as Republicans.

"He cut across party lines," said Rep. Barbara Mikulski (D-Md.), one of several Maryland politicians who seek to claim Mathias' seat. "No other Republican had the appeal he did."

Though Mathias' independent brand of Republicanism cost him a key leadership post when his party captured control of the Senate six years ago, many of his GOP colleagues traveled to Baltimore aboard a special train to fete him tonight.

Senate Majority Leader Robert Dole (R-Kan.) joked about Mathias' independence in brief remarks. "When I go to Mac and say 'Mac, can you help me on this?' Mac says 'No,' " said Dole. "Mac's reached across both parties over the years. He set an example for us on civil rights."

Mathias' longstanding championship of civil rights was raised by several speakers, including Benjamin Hooks, the head of the NAACP, and Juanita Jackson Mitchell, wife of the late civil rights leader Clarence Mitchell Jr.

Mitchell recalled the time when Mathias, as a municipal attorney in Frederick, Md., agreed to desegregate a local theater in the early 1950s. Said Mitchell: "My mother said God has put His hand on the shoulder of that man."

Larry Simns, the head of the Maryland Watermen's Association, recalled that it was Mathias who secured legislation to pay for a federal study of the bay whose findings began the national and state effort to save the estuary. "He listens to me just like he listens to the governor of this state," said Simns.

Mathias said he would miss most the ability to "pick up the phone and do something for someone's life." He recalled a recent invitation to the 25th wedding anniversary of a former serviceman whom he had sprung from duty during the Cuban missile crisis so the man could get married. "The ability to do things is a great privilege," he said.

The Senate, said former colleague Howard Baker, "doesn't really lose people like Mac -- he'll be remembered."

Asked if he had any advice for someone retiring at the peak of his career, as Baker did, Baker replied: "A lot, but I'll give it to him in private. It boils down to: 'You'll like it. You'll like it.' "