The senior senator from Nebraska looks like the Midwestern candy and tobacco wholesaler he used to be -- a solid, earnest guy. But he is an avowed swinger, at least when it comes to voting.

He is by no means a flashy whiz-kid, or a golden-tongued orator like his fellow Nebraskan, William Jennings Bryan, nor is he acclaimed as a charismatic leader or for his intellectual brilliance. Edward Zorinsky in his first term has built his reputation mainly on being as hard to nail down as a Great Plains dust storm.

His political opponents say he's "inconsistent, ineffective and an opportunist." But, according to polls and talk in Nebraska, most of the home folks view him as their kind of guy -- hardheaded, independent, and about as effective as they can stand.

He is also known to many as an eccentric conservative so tight with a buck that he has made an annual ceremony out of returning to the U.S. Treasury money that he could have spent on staff salaries -- a total of $1.7 million so far in his nearly six years in the Senate. He's the one who had an aide steam unused stamps off the office mail, until he was informed that this particular little economy was illegal. And yet he has fought for higher price supports for farmers.

After they talk about his quirky style, however, people often add a comment like this one, from James Giltmier, an aide to Sen. John Melcher (D-Mont.), who has worked closely with Zorinsky on farm issues.

"Notwithstanding his bad-boy image, he's been pretty effective. . . . He's not thought of as one of the great statesmen, but -- what the hell -- he had to get elected in Nebraska."

The Cornhusker state is bedrock conservative, one of the few where there are more registered Republicans than Democrats. Its two previous senators are still remembered for, among other things, their die-hard defenses, respectively, of "mediocrity" (in the appointment of a Supreme Court justice) and of Richard M. Nixon (after the revelations of Watergate).

Zorinsky, 53, son of a Jewish Russian immigrant, ran the family tobacco and candy wholesaling business for 23 years before he won a post on the Omaha public utility board.

He went on to become a popular and successful mayor of Omaha. A lifelong Republican, when the local party hierarchy insisted on another candidate for the Senate in 1976, Zorinsky decided he'd rather switch than fight and ran and won as a Democrat.

He considered swinging back again when the Democrats lost control of the Senate in 1980, but he and the Nebraska Republican party leaders, who were unimpressed with his performance, were unable to work out a reconciliation.

One of his favorite sayings is: "There are too many Democratic senators, and too many Republican senators and not enough United States senators."

As a United States senator, he has been most visible as a key swing vote on major programs of two presidents. He also is credited with influencing various farm legislation, most notably in areas of credit and rural electrification.

And, as chairman of the Western Hemisphere subcommittee, had begun to carve out an unlikely niche for himself in foreign relations before his party lost control of the senate.

He was one of the Democrats who helped Reagan push his economic plan through Congress last year. And on the AWACS sale to the Saudis, after first opposing it, Zorinsky succumbed to heavy presidential lobbying and handed Reagan the key vote that put it over the top.

Zorinsky has supported Reagan more than any Democratic senator outside the South, according to Congressional Quarterly.

But he was also among those who pressured the president to lift the Soviet grain embargo and he reportedly worked hard though unsuccessfully behind the scenes to strengthen last year's major farm bill -- which he sponsored and then lambasted as a "turkey" -- on behalf of his farm constituents.

"I've seen him probably grow into the job more than anybody else on the Agriculture Committee," said Robert Mullins, chief lobbyist for the National Farmers Union.

"He's a compromiser in the best sense of the term. He's able to work out some very divergent views, and work out a consensus policy. . . . As the 1981 farm bill developed, Zorinsky offered some amendments. They didn't exactly fly, but he was able to bring things closer to his position than they would have been. . . . He's a workhorse, not a show horse."

He has also pressed for investigations of various instances of government waste. He recently held up a $4.8 billion foreign assistance bill, which was important to the administration, because defense officials wouldn't let him see a study on the issue.

He has attacked the military practice of leasing (instead of selling) equipment to other countries as a costly way of avoiding the need for Congressional approval. And he initiated an audit of the Federal Farm Insurance Corp. that got some free-spending officials fired.

According to Sen. Orrin Hatch (R-Utah), Zorinsky is most effective "as a coalition builder" and in his "bipartisan way of voting. He has the guts and will to stand up for what's right despite pressure from the Democratic Caucus."

However, even some of Zorinsky's political allies say they have been confused by the senator's stand on the Reagan budget -- supporting it, then criticizing it. And some also speak with puzzlement about the furrow he plowed through foreign relations, when he seemed to depart temporarily from the conservative straight-and-narrow and support aid to the Sandinistas in Nicaragua. He abandoned that position when Reagan took office.

And while some see him as a good "compromiser," others who have worked on legislation with him get tight-lipped and squinty-eyed at mention of his name and say things like, "He's tenacious when he gets his teeth into an issue. . . . He's not very compromising."

Under President Carter, he created a stir and angered White House aides by not only withholding his support for the Panama Canal treaties but revealing to the press the embarrassing details of the White House entreaties to him.

He also has a reputation for showing up at every free embassy reception in town and even at Burger King openings. Some see this as a logical extension of his penny-pinching nature.

Not so, says Zorinsky; it's all in the line of duty. He sees his involvement in foreign relations, including the embassy night life, as a natural extension of his interest in agriculture, because foreign markets affect the local ones.

"Sure, I go to embassy parties, because I'm a member of the Foreign Relations Committee. I go to Burger King because that happens to be a constituency of mine. We have lots of Burger Kings. . . . People from Nebraska were there and they expected me to be there. I don't do it because I need any more food, or I'm hungry."

It was in pursuit of fast food that the elusive senator recently threw a scare into medical personnel at George Washington University Hospital, where he had been admitted for tests in connection with a minor heart ailment.

Unbeknownst to his doctors, he and his wife decided to stroll out of the hospital to a nearby eatery, he said, for a hamburger. Trouble was, he still was wearing a monitor that measured his heartbeat and breathing. As he headed out the door, the blips on the monitor screen grew fainter and finally stopped registering. "They were beside themselves," he said of his attendants.

Zorinsky also has:

* Removed his office door from its hinges and invited anyone to walk in, anytime. "I never close the door on anything," he once said.

* Refused to accept the small lapel pin handed out to senators upon their arrival, because it was bought with taxpayers' money. Last November his wife finally bought it for him as a birthday present.

* Rejected the use of an automatic signature machine, preferring to sign all his own correspondence by hand.

The senator prides himself on having no administrative assistant.

Key Democrats, both in Washington and in Nebraska, talk about Zorinsky mainly as an organizing and fund-raising chip. Both parties welcome any vote when it comes to organizing the Senate.

That is one of his Republican opponent's chief points of attack on Zorinsky. James Keck, a former Air Force general, warns the home folks that they had better put a Republican in the Senate or they run the risk eventually of having Sen. Edward M. Kennedy (D-Mass.) as majority leader.

But Nebraskans, who have the only non-partisan legislature in the country, don't get too hung up on party labels. And they seem to like Zorinsky's style.

"A lot of us are that way ourselves," said Eugene Glock, an influential corn and soybean farmer in Rising City. "Few of us vote strictly party line. I think people respect Sen. Zorinsky for having the intestinal fortitude to at times buck the party. . . .

"Sen. Zorinsky at least gives the appearance of understanding our problems and trying to do something about them. . . . Of course, farmers these days are somewhat dissatisfied with all our representation in Washington."

Early polls showed Zorinsky leading with 53 percent to 17 for Keck.

Keck's supporters are buoyed, they say, by signs that Zorinsky's support is "a mile wide and a foot deep," meaning that polls show most of his supporters "barely agree with him."

Zorinsky "operates mainly from a visceral, instinctual level and he's got a good feel for what the people back in Nebraska want," said one of his former aides. "He gives them that feeling that he's working for them, rather than actually doing very much. . . . Someone who is not an activist is probably fine with them."

Both Democrats and Republicans in the state praise the senator's energy when it comes to getting home and keeping in touch with the people.

"He gets around pretty good and has been quite visible," said Republican Art Knox of Lincoln Steel, a national committeeman for Nebraska. "We've got our work cut out for us."

In their assault on Zorinsky, the local Republicans expect an assist from another politician who is popular in Nebraska -- Ronald Reagan -- either in personal campaigning or television commercials.

But Zorinsky says he's ready for that.

Across the bowl of home-grown popcorn on his office coffee table, the senator from Nebraska passes a thick sheaf of letters fanned out like a poker hand. They are on creamy White House letterhead, signed by Ronald Reagan, and they all express deep gratitude to Ed Zorinsky.

"Were I to take out a full-page ad and reprint all of his letters to me," says the senator, "I'm sure the people of Nebraska would understand that I haven't totally opposed the president. . . . I'll support him when I feel he's right, oppose him when I feel he's wrong."

At another point, he said, "I've been very independent-minded. . . . I voted against and have also supported administrations of the Democratic Party and also the Republican Party.

"Basically it's the ideology and philosophy of the mainstream of both parties that move a given piece of legislation."