James F. McGovern, staff director and chief counsel of the Senate Armed Services Committee, may leap across the moat between the legislative and executive branches and become undersecretary of the Air Force under Edward C. Aldridge Jr. If McGovern leaves the committee, staff member Carl M. Smith is expected to succeed him.

The prospective change comes at a time when Armed Services, chaired by Sen. Barry Goldwater (R-Ariz.), is feuding with the Senate Appropriations defense subcommittee, chaired by Sen. Ted Stevens (R-Alaska), over which unit has the right to earmark money for specific Pentagon projects. Last year, in a sharp break with congressional procedure, the appropriations subcommittee earmarked money for programs the Armed Services Committee had not authorized. One part of the feud will surface soon when members of the Senate Armed Services Committee seek through legislation to prevent Pentagon research funds from going to universities favored by seven influential senators, including Stevens, without being subject to normal competitive award procedures.

Lyng Team . . .

It has taken a while due to paper work and politics, but the brain trust that will guide the Agriculture Department under Secretary Richard E. Lyng is taking shape -- in large part through a game of musical chairs.

The Senate Agriculture Committee is scheduled to hear testimony today on the nominations of Peter C. Myers, a former Missouri farmer, as deputy secretary and White House staffer Chris Hicks as general counsel. Myers would replace western farmer John Norton, who quit in a huff earlier this year when the White House bypassed him for the top job at USDA. Hicks would replace Daniel Oliver, who left USDA to become chairman of the Federal Trade Commission.

President Reagan announced Monday that Myers' current position as assistant secretary for natural resources and environment will go to George Dunlop, an aide to Sen. Jesse Helms (R-N.C.) who since 1981 has been staff director of the Senate committee. In his new job, Dunlop would oversee the Forest Service -- the largest USDA agency -- and the Soil Conservation Service.

Sources report that Kathleen W. Lawrence, deputy undersecretary for small community and rural development, has the inside track for nomination by the president to succeed Frank Naylor, her boss. Naylor is moving to the top post at the reorganized Farm Credit Administration, with a Senate committee vote on his nomination set for this morning.

Still to be filled is the job of assistant secretary for marketing and inspection services. Former North Dakota grain trader Richard W. Goldberg, a deputy undersecretary for international affairs and commodity programs, and Kenneth A. Gilles, head of the Federal Grain Inspection Service, are reportedly under consideration to replace Raymond W. Lett, who left USDA earlier this year.

Critical Mass . . .

Former secretary of health and human services Margaret M. Heckler may have a slightly lower profile in Washington now that she's U.S. ambassador to Ireland than she did in her final stormy days at HHS, but she's managed to stir a small controversy in the pages of Variety.

Theater critics on the Emerald Isle are up in arms, according to Variety, over Heckler's review on a top-rated Irish radio talk show of a new production of "Philadelphia Here I Come" at a Dublin theater.

"Critics did not resent the appearance of the ambassador," wrote the trade magazine, but apparently she did violate a cardinal rule: instead of covering the play on opening night, she reviewed a preview of the show, thus beating out Dublin's more established critics.

Constitutional Candy . . .

Obsolescence in the defense of liberty is no vice.

The lavish four-color 1986 wall calendar issued by the Commission of the Bicentennial of the United States Constitution includes a page listing "Planned Event for 1986" in early celebration of the Constitution's 200th anniversary. Most listings concern such sober enterprises as the Army's plans to develop a series of brochures concerning signers of the Constitution who fought in the Revolutionary War and the Library of Congress' sponsorship of a supplement to "The Records of the Federal Convention of 1787."

Enter the Daughters of the American Revolution, who have designed not only a commemorative medal, a logo and a pin, but also a "bonbon dish."