It should be campaign time here in southside Virginia's Fifth Congressional District, but you'd never know it by following Rep. W. C. "Dan" Daniel around.

The congressman, a tall, silver-maned former cotton mill executive who has represented this conservative, largely rural area for 12 years, has no media consultant, no polls, and no television ads -- in short, none of the familiar trappings of American politics in 1980.

The candidate never asks for anyone's vote nor even mentions his reelection, a subject that bears one similarity to death: It's so inevitable that no one much bothers to talk about it.

That's because Daniel, who calls himself a Democrat but votes the way Ronald Reagan might were he in Congress, has no opposition -- a luxury Daniel has enjoyed in each of his last five elections. He is so entrenched that when the GOP's district chairman had the temerity earlier this year to form a committee to find someone to oppose Daniel, party members responded by electing a new chairman.

Daniel's seat may be one of the nation's safest, but it is hardly exceptional. For while incumbents in the Washington suburbs fight for their political lives every two years in increasingly bitter and expensive struggles that capture the headlines, in the rest of the nation many members of the House of Representatives can still count on a free ride when election time rolls around.

"There may be an opponent on the ballot, but at most one out of three House races are seriously contested in a given year," says Michael Barone, vice president of Peter D. Hart Research Associates in Washington and coauthor of "The Almanac of American Politics."

Of Virginia's 10 House seats, for example, only Northern Virginia Reps. Joseph Fisher and Herbert Harris face tough, well-financed challengers. Three other incumbents have no opposition and four face token or long-shot opponents. In Richmond, where incumbent David E. Satterfield decided to retire, the Republican candidate is considered a virtual shoo-in.

In Dan Daniel's case, his highly conservative voting record, close ties with area Republicans and the business community and strong emphasis on constituent services all have combined to make his seat virtually impregnable.

In return for the unusual loyalty he enjoys from the opposition party, Daniel does things most politicians don't. He maintains a studious neutrality in national and state elections, for example, never even revealing how he casts his vote.

All of which does not sit well with many of the district's more partisan Democrats. They suspect that Dan Daniel, who was one of Richard Nixon's closest congressional friends, is a Republican in Democrat's clothing.

"Dan runs as a Democrat and I wish he'd vote like one," complains former Henry Country Democratic chairman James Martin. "But 80 percent of the time he's more like a Republican."

At the least, as Daniel's voting record reveals, he is a throwback to the Dixiecrats of the 1950s, Southerners who ran as Democrats but usually voted with a conservative coalition, especially against civil rights legislation sponsored by Democrats. That makes him a dying breed in Virginia as well, where, with Satterfield's retirement, Daniel will become the last of the old-time conservative Democrats.

It is a distinction of which the amiable Daniel, who turned 66 last May, is well aware. He says he realizes it is highly unusual for a politician to call himself a Democrat who annually scores a zero rating from the liberal Americans for Democratic Action. He also ranks 90 to 100 percent on the legislative report card of its conservative counterpart, Americans for Constitutional Action. But he is not shy in explaining why he stays in the party: seniority.

"My feeling is most of the Democrats left me, I didn't leave them," says Daniel. "Seniority doesn't have the meaning it used to have, but it's still an important factor in Congress and I can better serve the people of my district by staying a Democrat."

Dan Daniel not only represents his congressional district, in many ways he epitomizes it.

The Fifth is a stronghold of lower-middle-class voters who wear blue on their collars and patriotism on their sleeves. Census figures show that more than 60 percent of the district's workers hold blue-collar or service jobs. Median family income as of 1970 was $7,471 -- just slightly more than half that of Northern Virginia's affluent Tenth District. Median education ends after the ninth grade here, and it was one of two Virginia districts to give George Wallace a plurality in his 1968 presidential bid.

Like those of his constituents, Dan Daniel's roots are working class. The son of a sharecropper, he had to quit school after the eighth grade. He started his career at Dan River Mills, the area's largest and most influential employer, as a mill hand, eventually working his way up to assistant to the chairman of the board. A World II veteran, he also rose through the ranks of the American Legion, becoming national commander in the late 1950s.

A Byrd machine loyalist, Daniel managed Harry F. Byrd Jr.'s successful first Senate campaign in 1966. Two years later, he was the organization's hand-picked choice for the Fifth District seat. Backed by corporate interests, he amassed a $24,000 campaign war chest -- big money then in the Fifth -- and took 60 percent of the vote in a three-way race against a Republican and an independent.

"Dan was flying around campaigning in the Dan River Mills company airplane while Weldon [Tuck, his Republican opponent] and I pushed our cars from town to town," recalls Ruth Harvey Charity, the independent opponent.

Charity and other blacks, who make up nearly 30 percent of the district's population, say Daniel has all but ignored their needs and has voted against every major piece of social legislation that might aid blacks and the poor. But even they concede he is virtually unbeatable because he has tended so well to the problems of individual constituents.

"When you've got a problem with Social Security or the VA, his office will help you," says Charity. "A lot of people don't care how he votes on civil rights legislation or the Voting Rights Act as long as they get their Social Security checks on time."

Last Friday was typical for Daniel's local office, which he tries to visit at least once a month even when Congress is in session. Playing the role of social worker more than legislator, he listened to complaints from nearly two dozen constituents. One woman wanted help in obtaining GI benefits for her mentally disturbed son, a Vietnam veteran. A man with brown lung disease wanted to get a bill collector off his back. A prominent local matron bemoaned new federal regulations that may force her to integrate her local homemakers club.

Each supplicant got a sympathetic hearing and a promise to help from Daniel's staff of 12, which, like most congressional offices, includes a full-time case worker.

"Dan Daniel really excels at that kind of service," says state Del. Mary Sue Terry (D-Stuart). "Write him a letter and I guarantee his office will get you an answer within 48 hours."

On Capitol Hill, Daniel is largely an anonymous figure, often confused with Republican Rep. Robert Daniel of the neighboring Fourth District. Both men share conservative philosophies and have seats on the House Armed Services panel. Dan Daniel also chairs two key subcommittees, including one that oversees $10 billion annually in "non-appropriated" military funds.

The folks back home don't seem to mind that Dan Daniel is not one of Washington's movers and shakers. They are more interested in the fact that he has voted for every major defense appropriation bill in the last decade.

"These people honor the flag and they believe in a strong defense," says Del. Frank Slayton (D-South Boston). "They identify with Dan and the positions he stands for."

Slayton is one of a large group of aspiring politicians mentioned as a possible successor to Daniel when he retires. There were rumors he would quit this year but now that they have proved wishful thinking, many are hopeful he will follow his colleague Satterfield into retirement in 1982.

"Anybody who thinks that doesn't know Dan Daniel very well," says legislative aide Terry Hoye. "He loves his work."

Since he has not faced opposition in so long, no one here can be positive of Daniel's political strength. But no opponent seems to want to find out.

"He's got the corporate power behind him," says old foe Charity. "That is the reality and the reality is that until Dan decides to retire or the good Lord asks him to come up and help Him, he'll be in the seat."