This 25-year-old aircraft carrier and Vice President Mondale met on the Delaware River near Philadelphia today to demonstrate that some political promises are kept.

The Saratoga arrived from duty in the Mediterranean for a $526 million, 28-month overhaul at the Philadelphia Naval Shipyard.

Mondale came from the White House lest anyone forget that the Carter administration worked hard to bring carrier maintenance here, rather than to Newport News, Va., in part to make up for a 1976 Mondale promise it broke.

Mondale won cheers, and undoubtedly some votes, with the 1976 campaign pledge to reverse the Ford administration decision to close down the Frankford Arsenal.

A few months after taking office, the Carter administration found it agreed with its Republican predecessor, and the arsenal, which employed 2,000 workers, was ordered closed.

To the howls of pain from the depressed Delaware Valley region, Carter responded with a new promise -- that the Saratoga and three more carriers will be sent here for the extensive overahaul the Navy calls the Service Life Extension Program (SLEP).

The economic importance of carrier maintenance to this region was made clear by the presence of both Pennsylvania senators, both New Jersey senators and Sen. Joseph R. Biden Jr. (D-Del.) on the hangar deck with Mondale today.

The navy yard is in the district of Rep. Michael O. (Ozzie) Myers (D-Pa.). The congressman, who faces possible expulsion from the House Thursday for taking bribe money in the FBI's Abscam investigation, was not in the lineup of politicians here today.

"There's simply no way that we can exaggerate the importance of this visit," Biden said in a lengthy speech that was aimed at least as much at the TV cameras recording the Saratoga's welcome as at the assembled members of the Saratoga's crew.

It appears that, great as the impact will be, it has already been successfully exaggerated by the politicians.

The rehabilitation of the Saratoga is intended to extend its lifetime 15 years -- half the life of the average carrier -- at a quarter the cost of building a new carrier.

The navy yard has already hired 700 new workers, and will add about 300 more for the Saratoga. Subcontracts worth almost $6 million have been awarded in the tristate region, and the roughly 1,500 men of the Saratoga with their families will be buying their groceries and other goods here for almost three years.

A 1978 study predicted even greater benefits. According to The Philadelphia Inquirer, more than 2,000 civilian jobs would be added at the shipyard, subcontracts would total $50 million and the Navy would boost its personnel here during the overhaul by 2,900, not 1,500, according to first estimates that set the region aglow with anticipation.

The argument over just how much the region benefits from having SLEP performed here is likely to continue after the Saratoga has sailed back to sea. In any case, 4,800 jobs are likely to have been created and about $100 million additional dollars spent before another plane touches the Saratoga's flight deck.

Carter narrowly won Pennsylvania in 1976 thanks in good part to a large majority in Philadelphia. He also won Delaware, though he lost New Jersey to Ford.