From the day freshman Rep. Constance A. Morella (R-Md.) reported for work in January, House Minority Leader Robert H. Michel (R-Ill.) understood she occasionally would have to "stray from the reservation" to survive politically in her upscale, predominantly Democratic district.

But Michel probably didn't realize just how soon or how far Morella would stray. During her first six months in office, Morella has broken with the White House and the House GOP leadership on every major issue to come along, with the exception of trade.

Morella, whose 8th District includes most of Montgomery County, was the only freshman Republican to vote in March in support of a six-month moratorium on $40 million in aid to the Nicaraguan contras, a largely symbolic slap at President Reagan's Central American policy.

She voted to override presidential vetoes of the clean water and highway construction bills, as did many other Republicans, and then voted with the Democrats to approve a $9 billion fiscal 1987 supplemental spending bill -- a measure that only two other Republicans supported. She voted with the Democrats to cut $500 million from Reagan's Strategic Defense Initiative, after vigorously defending SDI research during her campaign.

Last Tuesday, Morella was one of only three Republicans to vote in support of a $1 trillion budget for fiscal 1988 that would raise taxes by $19.3 billion, cut military spending and repudiate many of the administration's spending priorities.

The budget, a compromise between House and Senate Democrats that was bitterly denounced by Reagan and GOP congressional leaders, was approved by a vote of 215 to 201.

"I went for it because it was a budget that looked to how we could cut programs and how we could build in terms of reducing our deficit," Morella said. "We've pretty much exhausted our domestic cuts. As Shakespeare said in one of his plays, 'Action is eloquence.' We must move forward."

More to the point, the budget is favorable to her suburban Washington district, which is home to a large number of federal employes and retirees. The budget protects cost-of-living adjustments and health benefits for retirees and assumes a 3 percent pay raise for federal workers. It also calls for increased funding for AIDS research, catastrophic health care and infant feeding programs, all popular programs in the 8th District.

"It was not an easy vote, but it's one I felt was best for my constituency," Morella said.

Michel said he understands Morella's predicament, adding that "It's very important that she votes her district.

"I've really not bored down on her like I would with other members," he said. "For freshmen, I don't believe there has to be that blood oath to be partisan. I give them the benefit of the doubt. As they build up a little seniority and they can take the heat, the tempo picks up."

Morella, 55, an engaging former English professor and member of the Maryland House of Delegates who frequently quotes Shakespeare at political events, clearly is compiling a voting record that plays well in her district, with its long tradition of ticket-splitting and moderate-to-liberal politics.

Last fall, she came from behind to defeat Democratic state Sen. Stewart Bainum Jr., a millionaire businessman, in an election to succeed Democrat Michael D. Barnes, who gave up his seat to run for the U.S. Senate.

Morella the campaigner offered voters a blend of liberal social philosophy and conservative views on fiscal and defense issues. She closely identified with the political tradition of former senator Charles McC. Mathias Jr. (R-Md.) and former representative Gilbert Gude (R-Md.), popular Republicans whose moderate politics have been the most successful for GOP candidates in heavily Democratic Maryland.

The Democratic Congressional Campaign Committee has targeted her for defeat next year, but many Democrats concede it will be extremely difficult to unseat Morella, a tireless and charismatic campaigner.

"She'll be very tough for the Democrats to move out of there," said Bruce Adams, a Democrat on the Montgomery County Council. "She's too savvy to make an error, and too conscientious."

But Adams and other 8th District Democrats question whether a moderate Republican who repeatedly breaks with her party can hope to gain influence and clout in the Democratic-controlled House -- also one of her biggest problems when she was in the overwhelmingly Democratic Maryland legislature. They recall Barnes' success in influencing the national debate over U.S. policy in Central America as chairman of the House Foreign Affairs subcommittee on western hemisphere affairs.

"Mike Barnes set a standard of bringing the 8th District national leadership," said Lanny Davis, a lawyer and Maryland's Democratic national committeeman. "I do not believe, as hard as she may try, that Connie Morella will be able to come close to meeting that standard. If we can find a Democrat who can unite the Democratic Party, I think she can be beaten."

A congressional aide who follows Montgomery County politics closely described her as "a minority of a minority" who is "caught between the demands of the Republican leadership and her district."

State Sen. Howard A. Denis, a Republican from Montgomery County in the same mold as Morella, disagrees, saying that Morella already has forged important ties with Republicans and Democrats in the House and has proved to be effective at constituent service and guarding her district's interests.

"Her concentration on local issues is of tremendous benefit," Denis said. "I don't see her as trying to be secretary of state. She's trying to be an ombudsman for the county . . . . People talk about a Mathias tradition. Before long, people will be talking about a Morella tradition."

Rep. Trent Lott (R-Miss.), the House minority whip, said Morella has spent considerable time on the floor, shepherding through ceremonial resolutions and learning the ropes. "Connie is proving already she's a very capable legislator," he said.

Morella serves on the Post Office and Civil Service and the Science and Technology committees, both important to a House member with a district that contains a large concentration of federal workers and retirees and scores of high-tech companies along the I-270 corridor, including Martin Marietta, IBM and Fairchild.

As a member of the Science and Technology Committee, Morella is part of the debate over whether Congress should authorize $12 billion or more for a space station and more than $4 billion for a giant atom smasher known as the Super-conducting Super Collider. Both projects could have important financial implications for her district.

Also, she is a member of the Select Committee on Aging and serves on the executive board of the Federal Employees Task Force, with oversight of pay scales and working conditions of federal workers.

Morella requested congressional hearings on the administration's controversial proposal for mass drug testing of federal workers. She condemned the plan as "both demoralizing and ridiculous" and later voted for an amendment to a spending bill to block its implementation.

Morella portrays herself as an independent thinker, not a maverick, and is careful not to attack House GOP policies she disagrees with. By her own count, she has differed with the administration on 60 percent of all votes.

In almost every case in which she has differed, she said, "There were other Republicans who felt the same way, which indicates there is a range of beliefs in each party . . . . You represent your constituencies and your conscience."

Morella sided with the president in voting against the omnibus trade bill April 29 because of an amendment introduced by Rep. Richard Gephardt (D-Mo.) that would require tough retaliation against countries that continue to use unfair trade practices to gain huge trade surpluses.

"I would have voted for the trade bill, but the Gephardt amendment made it impossible for me to do so," she said. "By adopting this amendment, the House substituted protection for competition, thus sending the wrong signal to the world's trading nations."

She also went along with the administration by voting May 5 for an amendment to boost the borrowing authority of the Federal Savings and Loan Insurance Corp. from $5 billion to $15 billion. The amendment, aimed at increasing the FSLIC's ability to recapitalize failing savings and loans, was rejected by the House.

In supporting the six-month moratorium on aid to the contras, Morella joined 16 other Republicans in opposing the president's efforts to pressure the Marxist government of Nicaragua. Morella said she considers the ruling Sandinistas a "threat" to Central America and favors funneling aid to more democratic governments in that region.

"My frustration is the administration doesn't have a clear-cut policy in the region," she said. "If they want to get {the Sandinistas} to the negotiating table, military aid to the contras won't get them to the table."

During her campaign, Morella defended humanitarian aid to the contras, saying it was appropriate if properly administered. "She saw the winds on that and moved accordingly," said a former aide to Barnes who approved of her vote. "It was an indication to me she was moving to the constituency."

In May, Morella and 19 other Republicans cast votes that were decisive in reducing SDI funding in the next fiscal year from $3.6 billion to $3.1 billion. The amendment passed, 219 to 199.

Last fall, Bainum criticized Morella for her support of research projects for the president's "Star Wars" program. At the time, Morella characterized SDI as "an enormous step forward for peace" and an effective "bargaining chip" in arms talks with the Soviet Union. Morella said recently that she never considered deployment of SDI feasible but felt that many beneficial "spinoffs" could come of continued research.

"I don't see any future for deployment," she said. "It's costly and it won't work . . . . Then again, the Soviets still harbor enormous concerns about it. It has been an enormous bargaining chip."