He comes off like Jimmy Stewart in "Mr. Smith Goes to Washington" -- bigger and beefier and all that, but talking in this earnest drawl, sincere as all get-out, the innocent abroad.

"Boy, I'll tell you," said George Hansen on his way back home from a quick trip abroad. "You sure do feel a little noticeable over there. You kinda stand out. Of course, we're taller than they are, you know. But you just have to get out and mingle and tell 'em what you need and try not to act like a sore thumb."

Sometimes, as the 6-foot-6 Republican representative from Idaho comes forth with these kinds of wide-eyed impressions, it's easy to forget the man is talking about mingling with mobs on the streets of Tehran. That this is the guy who hopped a plane and set up shop in the Intercontinental Hotel -- talking to Iranian officials, giving round-the-clock press interviews -- and got into the American Embassy to become the first American to see the hostages.

Mr. Smith goes haywire?

At least, that's the way the White House and the State Department and a number of Hansen's colleagues have looked at his trip. Unhelpful, said Jody Powell. "Out of bounds," said House Speaker "Tip" O'Neill. "Dangerous and irresponsible," said Millicent Fenwick (R-N.J.). And those were the ones being quoted by name.

Then there was the Republican leader who said he held his breath the whole time Hansen was in Iran, fearful of what he might do over there. And the sign that appeared in the men's room at the Capitol announcing that buses would be departing at 5 p.m. for Dulles Airport to greet Hansen and promising free beer, the Marine Band and remarks by Henry Kissinger. $ it doesn't bother George Hansen one bit. "I think Jody Powell and Tip O'neill and some of the others who have had something to say about this might take a trip over there and get their own licks in for mercy instead of trying to detract from the rest of us who are doing these things."

Except, of course, that no one else is doing these things and a lot of people wish George Hansen hadn't.

Still, the wonder of the thing amazes. Ramsey Clark didn't get anywhere. Andy Young was convinced not to go. And here comes Hansen, who was sitting around with an aide one night thinking about calling the Iranian Embassy to see what evidence they had on the shah. All it would cost was a phone call, said his legislative aide, Arlen Withers, and the next thing he knew, Hansen called him from Germany a week later.

"I thought, 'Here we go again,'" said Withers. "The congressman just likes a challenge. He gets really bored when things are running quietly."

The congressman looked pale and drawn on the drive back from Dulles, and his dark, slicked-back hair was, as his wife Connied quietly suggested, in need of a haircut. He hadn't slept more than two hours at a time in Tehran, what with the media calls from everywhere from Sydney, Australia, to Spokane, Wash., and the meetings with Iranian officials at all hours, and the trip to see the hostages, and the stories about the shah.

"It was just one thing after another," he says, almost with surprise. "I've never been so busy in my life. I've never had so much to do."

There was the Iranian official who broke down and wept as he told him about living in America and wondering why the letters from a relative had ceased, only to find his relative had been assassinated by the shah. There was the look of the city itself -- "I can tell you Iran certainly has a westernized element. Everywhere you look there's a Kentucky Fried Chicken stand." Everywhere you look, he says, there are the signs of half-finished progress -- "You see huge, huge apartment complexes going up, they look like a mountain out there on the prairie, and they're not going anywhere." Idaho may not be Iran, but a prairie is a prairie.

Hansen is having second thoughts about the shah. "I think the shah had a good public-relations effort in this country. You had all the makings, in a sense, and I don't mean to suggest that it was artificial necessarily, of the Hollywood thinking of the shah of shah and the king of kings."

Hansen was blindfolded before he was brought in to meet the hostages, stumbling around the compound as they shoved him into the car that took him to the place where they were held. He was scared. "When they shut those gates behind you and they admit you alone . . . you wonder how final that is."

There were, he says, "Some touching stories and some cute stories, I guess. One great big strapping Marine with shoulders big enough to play with the Los Angeles Rams, I patted him on the shoulders and remarked about that and I said, 'Your shoulders are still in condition.' and he said, 'Yes, sit, I do my pushups every day, sir.'"

The weirdness element keeps getting bigger as Hansen talks -- Marines doing pushups and fast-food franchises, while countries stand in dark shadows and disaster haunts the headlines. There's George Hansen working the mob, like he was running for the Revolutionary Council, shaking clenched fists, giving impromptu interviews on the street, dominating Iranian prime time. One day, in his honor, the crowd was even dissuaded from burning a flag.

"I've been accused of being a big friendly individual," says Hansen modestly. He's also been accused of violating campaign finance laws. And pleaded guilty to two misdemeanors -- faailing to file one report on campaign financing and lying on another. The violations, his aides say now, were unintentional. But there is one aspect of it all that has continued to haunt him: his attorney's argument to the judge that the reason Hansen should not be sentenced to a two-month prison term was that "Congressman Hansen was stupid but he wasn't evil."

"Sometimes," laughs Hansen's legislative aide, "I think that lawyer should have been stood up against a wall and shot for saying that."

Sometimes, says a colleague of Hansen's in the House, "the only way you can describe this guy is a loose cannon."

A wide-ranging one, anyway. Last summer there was the trip to Nicaragua to let the soon-to-be-ousted dictator Anastasio Somoza know that the United States was behind him. Last January it was Taiwan, promising the Taiwanese that they would get "the final equipment necessary to take care of the atomic program that you have started . . . " And the last-ditch effort to block the Panama Canal treaties after the Senate passed them.

There is controversy and criticism, but Hansen presses on. The descendant of Mormon pioneers, he thinks religion has something to do with it. dAnd the Idaho influence -- "The West is an independent area," he says. "People say what they think and, representing people like that, I think it's important that I do what I think is right. Some people call it meddling, but if I can bring a ray of hope and that's meddling, we need more it."

His wife Connie, pale and porcelain, watches him protectively as he rushes in and out of his office to meetings on his first day back. His unpaid administrative aide, she usually comes in with him at 5 a.m. and leaves late in the evening. While here husband was gone she monitored the telephones day and night, listening to praise and condemnation, soothing the relatives of hostages who could call in to learn what her husband had discovered.

The pride in her husband is unflinchiing. "george has never been one to spend time deliberating," she says.

"He just does what he can to help."