Presidential candidate Walter F. Mondale, who spent a hectic day in Maryland last fall to help reelect the Democratic ticket headed by Gov. Harry Hughes, had the favor returned today.

When Mondale arrived in Annapolis, this time to kick off his Maryland campaign for president in 1984, Hughes convened a special joint press conference to laud the former vice president and issue an "unqualified" endorsment of him.

Hughes is the second governor, after Minnesota's Rudy Perpich, to sign onto the Mondale effort, and his announcement--nearly 14 months before the state's presidential primary--completed a clean sweep of support for Mondale from the state's top Democrats.

"This has been an absolutely spectacular day for Walter Mondale," said Mondale as Hughes finished his endorsement. "Thank you very much for delivering one of the finest speeches ever heard."

If the endorsement was the highpoint, it was also the theme of the afternoon and evening Mondale spent in this liberal Democratic state, one of six states that voted for the Jimmy Carter-Mondale ticket in the 1980 Ronald Reagan landslide. Mondale's purpose today was not to meet the voters but to meet the state legislators, money-raisers and others who get campaigns moving.

Mondale has been organizing in Maryland more than other Democrats running for president and has won the support of most of its leaders. Hughes, Lt. Gov. J. Jospeh Curran Jr., U.S. Sen. Paul S. Sarbanes, Attorney General Stephen H. Sachs and, in more carefully guarded words, Comptroller Louis L. Goldstein have all given their support. U.S. Reps. Michael D. Barnes of Montgomery County and Barbara Mikulski of Baltimore also have come out for Mondale.

Everywhere he went today, Mondale was on the attack against the Reagan administration.

"Ronald Reagan in four years has added more to the federal debt than all presidents since George Washington walked through this building," he said at a press conference in the historic statehouse where Washington resigned his commission as commander-in-chief of the Army.

Flanked by flags at the press conference and backed by a blue bunting for photographic effect, Mondale also spoke of the need for "scaling back the defense budget to reality" and pushing for legislation to contain spiraling hospital costs, and again said he opposes a constitutional amendment to balance the federal budget.

In a speech to members of the legislature, who have cut state budgets because of federal aid cuts, Mondale criticized the president's "new federalism" program. New federalism, he said, has "returned billions and billions of dollars of responsibility to the states without transferring one dime of actual money."

And at a reception for the United Women's Democratic club, he said that he, unlike the Republican administration, would stand by the Equal Rights Amendment, making it a priority of his administration.

After the Annapolis events, Mondale traveled to a catering hall in Baltimore County where his campaign held a small $500-per-person cocktail party and a $100-per-person dinner. Just over a month ago U.S. Sen. John Glenn, another Democrat running for president, was present at a similar affair in which the proceeds went to the state's Democratic Party.