It was crunch time yesterday as the White House made one last pitch for its endangered contra aid package, and Rep. Roy Dyson (D-Md.) decided to take advantage of the president's desperate political straits.

The price for his vote in favor of the $36.2 million package, Dyson bluntly told President Reagan during a White House meeting, was agreement by the administration to scrap plans to phase out a squadron of submarine-communicating aircraft at Maryland's Patuxent Naval Air Station.

"If you want {support for the contra aid package}, that's what I want," Dyson recalled telling Reagan. " . . . I'm waiting for a call."

The final days of lobbying preceding today's scheduled House vote on contra aid have been fierce, many agree, and House members from Maryland and Virginia said they have felt the heat as well as the sweet sensation of being courted.

Citizens for Reagan sent letters to financial supporters of Rep. Constance A. Morella (R-Md.) -- including her mother -- asking that they urge Morella to change her mind and vote in favor of aid for the Nicaraguna rebels. At a recent Republican gathering in Potomac, a contra aid supporter accused Morella of being a communist sympathizer.

Rep. Owen Pickett (D-Va.), who is undecided, has been swamped with letters and calls from around the country demanding that he vote with the president.

"We've been getting about 50 calls an hour," said William Hart, Pickett's administrative assistant. "It's like noise on the line. You pick up the phone, it's some guy from California, and he's saying, 'I want the congressman to vote against contra aid.' "

Rep. Benjamin L. Cardin (D-Md.), who is closely allied to the House Democratic leadership in opposing additional contra aid, said his office had received calls from the White House, including one from White House chief of staff Howard H. Baker Jr. that Cardin missed.

"It's a full court press," Cardin said.

Reagan's $36.2 million aid package includes $3.6 million earmarked for lethal aid. The rest is for nonlethal assistance, which the administration defines as anything but "weapons, weapons systems and ammunition." Under the president's proposal, the lethal aid would be placed in escrow during March and then released if Reagan certifies that a ceasefire in Nicaragua is not in effect.

House Democratic leaders predicted this week that the aid package will be rejected. However, others say the outcome still is in doubt and could be determined by a handful of wavering Democrats and moderate Republicans who might succumb to Reagan's last-minute entreaties.

Countdown '87, an umbrella group of about 15 national organizations and church groups, has led lobbying against the measure. Since mid-1987, the group has generated about 80,000 letters and 25,000 calls to targeted House members, urging them to vote against the aid package, a spokeswoman said.

"We're not trying to electorally jeopardize anyone, but to let Congress know the depth of opposition to contra aid," said Rosa DeLauro, executive director of Countdown '87.

Any sign of wavering or indecision by a House member has triggered a deluge of calls and letters from lobbyists. When word spread recently that Rep. Tom McMillen (D-Md.) was undecided, proponents and opponents bombarded his office with calls and letters.

"It's just amazing. It's like nothing I've seen before," said Sarah Geithner, McMillen's legislative assistant.

Yesterday, McMillen said he had decided to vote against the aid package, largely because of his dissatisfaction with the provision that would allow the president to determine whether to release lethal aid.

McMillen said that if the president is the "adjudicator of whether progress is being made," then a breakdown in the peace process might become a "self-fulfilling prophecy" of the Reagan administration.

Rep. Norman Sisisky (D-Va.) said he probably would vote in favor of the aid package. But he acknowledged that, in the face of contradicting statements by the White House and contra aid opponents, "You just don't know if you're right or wrong."

Morella, a Montgomery County Republican who frequently has broken with the White House on key issues, said she agrees with leaders of the five Central American countries pursuing a regional peace plan, who say additional aid for the contras would be destabilizing.

"The administration and Congress could come up with a different strategy," Morella said. "I think we should give peace a chance and not give {Nicaraguan leader Daniel} Oretega an excuse" to back out.

But Rep. Beverly B. Byron (D-Md.), a member of the Armed Services Committee who visited Nicaragua last weekend and met with Reagan yesterday, said she favors additional contra aid to keep pressure on the Nicaraguan government.

"I'm convinced the aid to the contras has been beneficial," she said. "I also feel . . . that for the contras to be as far inside the country as they are, there has to be some fairly substantial support for them within the peasant population."

Of the remaining House members from Maryland, Republican Rep. Helen Delich Bentley is leaning in favor of contra aid and Democrats Steny Hoyer and Kweisi Mfume are opposed. In Virginia, Republican Reps. Herbert H. Bateman, Thomas J. Bliley Jr., D. French Slaughter, Stan Parris and Frank R. Wolf support additional contra aid, while Democrats James R. Olin and Frederick C. (Rick) Boucher oppose it.

Dyson, a member of the Armed Services Committee, consistently has supported aid to the contras until now. He recently caused a fuss in his Southern Maryland and Eastern Shore district by refusing to meet with Eric and Carol Schneider, peace activists from Prince Frederick, Md., who are lobbying against contra aid.

Last week, Eric Schneider, an oceanographer, and his wife, a nurse, began a fast and daily vigil at Dyson's Washington office, saying they wouldn't stop until Dyson agreed to meet with them. "We're his constituents," Eric Schneider said. "This is really unheard of."

Dyson agreed to meet with the Schneiders yesterday afternoon. Dyson said he had been too busy to meet with them earlier.

"Frankly, he {Schneider} has been a little obnoxious," Dyson said.