On a recent day, Joseph Alexander was up at 6 a.m. The Fairfax County supervisor arrived at his Lee District office at 7:30 a.m., where he opened mail from his constituents for half an hour before walking across the street and donning a blue smock to check his hardware business.

By 9 a.m., he was at a Metro board meeting where he often is an outspoken member. And by 2 p.m., he was in his 14th-floor office at Washington-Lee Savings and Loan Association, where he serves as vice president for marketing.

At 47, Alexander likes to consider himself a citizens' politican who is able to deal with such mundane governmental functions as fixing potholes and providing more sidewalks and street lights.

He also likes to think of himself as one capable of making decisions about a $5 billion Metro subway system that the man he twice supported for governor, Republican Gov. Mills E. Godwin, once called a boondoggle.

Through it all, Alexander, a Democrat, has managed to remain in public office for 14 years, becoming the senior member of the governing body of a county that he has seen grow from a rural stretch of pastures and cornfields to a continually developing urban jurisdiction with a population approaching 600,000.

His margins of victory in Lee District supervisor's races have steadily increased from 56 per cent in 1963 to 70 per cent the last time he ran two years ago. Some county politicans say they think he is unbeatable in his district.

"I think Joe, in his own sort of lowkey way, is the cosmic politician," said Fairfax Supervisor Alan H. Magazine (D-Mason). "The key to his success is getting involved with the bread and butter issues - he things that most concern people like filling potholes, getting sidewalks and street lights . . ."

Alexander says that in the last two years alone, he has had 2 1/2 miles of sidewalks installed in his district, 180 street lights erected and $1.07 million worth of sewer lines constructed. In addition, he said his district, which lies south of Alexandria, now has 1,865 acres of parks, an increase from 114 acres in 1964 when he took office.

"The job of the supervisor is to try to take care of the physical problems," Alexander said. "People want to get their tax money worth of services. There are people in the county who have been paying taxes for years. They see their real estate (taxes) going up. Their kids are grown and out of school. They want to know what they're paying their taxes for."

When Alexander first ran for county supervisor, he campaigned on one issue: gravel pits.

Lee District, which long-time residents claim had always been ignored, was the center for gravel pits in the county. As a result, residents there wanted more control over them.

Among the first things that Alexander did when he took office, was to see that the Board of Supervisors took over the policing of the pits. They formerly were under the control of the Board of Zoning Appeals, whose members are appointed by the circuit court in the county.

"He (Alexander) has a way of getting things done," said Supervisor Marie B. Travesky (R-Springfield).

Alexander's Lee District office is across the street from his hardware store on Franconia Road, convenient coincidence."

In fact, it was a bit more than that. It was Alexander who suggested that the county in 1971 purchase a tract of vacant property from the Franconia Volunteer Fire Department, in which he has been a long-time member.

The property, which the county bought for $90,000, now houses the county police substation, park polce and a tax assessment office in addition to Alexander's supervisor's office. The governmental center was built at a cost of $197,000 and opened in 1973.

Alexander has always been an advocate of police and fire services. A volunteer fireman since the age of 16, Alexander has often promoted efforts to get funds to hire additional firefighters and police officers.

When the supervisors recently discussed endorsing the concept of citizen anticrime patrols, Alexander said "Fairfax should hire more policemen to protect its residents. "I still think we have a responsibility to provide enough funds to protect the citizens, he said.

Alexander's concern for the 67,702 persons in Lee District has drawn praise at times. "He does one heck of a job representing his constituents," say Supervisor Audrey Moore (D-Annandale).

His concern for Lee District also has drawn criticism. "Joe is far more interested in the welfare of his own constituents than constituents of neighborning areas," said Del. Warren E. Barry (R-Fairfax), who represents Lee and other parts of southern Fairfax in the state legislature. "He goes to bat for them. Sometimes at the expense of other people in the county," Barry said.

Numerous county officials also privately question whether Alexander's position on the governing body of the fastest-growing jurisdiction in the Washington area and his job at an S&L that makes real estate loans in the county might constitute a conflict of interest.

Alexander served on the board of directors of Washington-Lee from January 6, 1964, until September 18, 1973, when he became the vice-president in charge of marketing.

He denies that there is a conflict of interest between his Fairfax and Washington-Lee jobs. He said he goes to great lengths to abstain from any county matters that might create a conflict.

Last year when the county housing authority was negotiating the purchase of a 37-unit condominium project from Washington-Lee, Alexander said he did not participate in the proceedings. He filed a disclosure affidavit to that effect.

Alexander abstained from voting when the supervisors approved the $1 million purchase.

"We're very happy to have him as an officer of our association," said Washington-Lee president Richard Lawton. He said Alexander is responsible for advertising, public relations and other administrative matters.

"I have a functional job," Alexander said of the part-time savings and loan job for which he was paid $17,000 last year. With his hardware store, Alexander is the only owner of a business on the county board.

Alexander doesn't like to talk about how much money he makes, shoving aside such questions with the response that his wife handles financial matters.

The supervisors are required by law to file copies of their latest income tax returns in the office of the board clerk. Although Alexander had not filed his when he was interviewed recently, he gave a reporter a copy of his 1976 return showing that he earned $44.833 from his hardware store, part-time supervisor's position, and the savings and loan.

Alexander says he grew up attending political functions with his father, Milton, who directs the motor vehicle violations bureau of the Fairfax General District Court and was a long time supporter of the Byrd Organization, the dominant political force in Virginia for many years.

Although his father is more conservative than Alexander, they annually host a political barbecue that attracts Democrats from throughout the state.

The younger Alexander describes himself as "a political moderate, but I'm not going to let progress pass me by."

"The thing about Joe is that he's a politician and proud of it," said one senior regional official who deals with him regularly. "He can be on one side of an issue today, and on the other side tomorrow and not be the slightest bit embarrassed that he changed positions. If there's a reason for him to change, he'll change."

He campaigned for Godwin when he ran as a Republican in 1973 against independent Henry E. Howell.

He supported Andrew P. Miller in his unsuccessful bid against Howell for the Democratic nomination for Virginia governor in June.

Now he said he supports Howell in the November election. "This is our opportunity to build a legislative foundation," he said. "We need a governor and legislature of the same party."