Denny Smith didn't run for Congress to become a long-term congressman. Although he spent $700,000 to get elected, his idea was "to come here and help and straighten things out" in a term or so, then return to his job as an Oregon newspaper publisher. The federal budget, he told constituents, could be balanced "just like you balance your checkbook."

Fifteen months after his election, Smith is a bitter man. "I can't believe that Ronald Reagan, the guy I campaigned alongside of, is the architect of a budget with a $100 billion deficit," he said. Last year Smith supported the president's program on every vote. This year, he called a news conference to propose his own plan to control spending.

"Reagan's robots." That's what the Democrats called Denny Smith and the 52 other GOP freshmen, the largest Republican class in a quarter century. Swept into office on a tide of fiscal conservatism, they voted in lock step for Reagan's budget and tax bills. Today they are on the verge of rebellion.

"The freshmen are more interested in Ronald Reagan's program than Ronald Reagan," said Hank Brown (Colo.), echoing the views of many first-termers who feel the president has broken faith and not cut spending enough. Brown, last year's class president, said Reagan should have vetoed all spending bills that exceeded the budget ceiling.

Conservatives join moderates in criticizing Reagan's defense increases. "I campaigned on the idea we could increase defense spending, cut taxes and balance the budget," said John Patrick Hiler (Ind.), one of the administration's most constant allies. "But it didn't occur to me that Reagan was going to raise the defense budget $60 billion in two years. Increasing military expenditures at the risk of the economy doesn't work."

A group of 21 GOP freshmen, led by Rep. Jim Dunn (Mich.) has called a press conference today to attack Reagan's proposed cuts in spending for education.

Another group, led by Rep. James K. Coyne (Pa.), is circulating a letter to Reagan saying they will vote against raising the debt ceiling because it would be "tantamount to an admission of failure in the fight to reduce spending, to control the deficit and generally to create a positive economic atmosphere for the hardworking American taxpayer."

That Reagan's budget is in trouble on Capitol Hill is hardly news. But that he should be losing the support of his most loyal troops, the men and women who campaigned for a "Reagan revolution," and who, for the most part, squeaked to victory on his coattails, is a measure of how far Republican unity has unraveled.

Cynics might attribute it to election year jitters, but the freshmen contend it is consistent with the brash idealism they expressed during their campaigns.

"A different kind of individual was elected in 1980," said Oregon's Smith, a 43-year-old political novice who ousted 24-year House veteran Al Ullman. "You might call us reformers. These 13 months have not necessarily been spent learning how to march. Some of us are trying to get hold of the handle of the drum so we can change the beat. The beat should be changed to balance the budget."

Smith has three pictures of Reagan on the wall of his cramped office in the Longworth Building. "I'm one of the president's strongest supporters," he said. But he adds, scarcely hiding his resentment, "I never went to a barbecue. All those people who didn't vote with him got wined and dined at the White House. All I got is a tie tack set."

Since last March, as unemployment in Oregon's timber country rose to record levels, Smith wrote repeatedly to the president urging a balanced budget to bring down interest rates. He could never get his letters past White House aides.

"The Palace Guard is pretty thick around the Oval Office," he said. "It's blocking information from the president about the severe situation the economy is in."

Nonetheless, Smith said, "I've been a salesman for the Reagan program. I still view my role as trying to live up to the promises the president and I both made." Smith's way of living up to them, he explained at his recent press conference, standing between an American flag and an easel full of budget charts, would be to freeze spending, including defense spending, at 1982 levels.

Then, he said, the 1982 outlay of $725 billion, would just about match projected 1984 revenues of $723 billion, thus balancing the budget.

"It's simplistic," Smith conceded. But, like a similar plan proposed the same day by Sen. Ernest F. Hollings (D-S.C.), it avoids the political trading that jacks up spending.

Far from being robots, the freshmen are a fiesty group, less concerned with politics as usual than their seniors. Brown, whose western Colorado district contains 80 percent of the nation's recoverable oil shale, is sponsoring a bill to abolish the $88 billion Synthetic Fuels Corp., which lends government money to private oil shale ventures. "Budget cuts, like charity, should begin at home," said Brown. (Reagan also declared himself opposed to "the administration subsidy of oil shale" during his campaign, but has since supported the Synthetic Fuels Corp.)

A 42-year-old Navy veteran who served in Vietnam, Brown campaigned for military budget increases. But he found himself voting with liberal Democrats to kill the defense appropriations bill because it exceeded the budget ceiling. "My dad is a disabled World War II veteran," he said. "I volunteered for Vietnam. I never thought I'd be voting against the defense budget. I voted against the B1 bomber, too. It has value, but we don't have the funds for it."

Brown, a cheerfully outspoken man, was a popular state legislator. Like many of his colleagues, he has been frustrated in Congress. "So much of our time is spent in puffery and so little in work," he said. "It's puffery to call recesses district work periods. Congress should work Mondays and Fridays. I'd have to stay here four years to cast as many votes as I have in one partial session of the Colorado assembly."

Colorado, he said, balances its budget by making conservative economic assumptions. Pulling a Wall Street Journal out of his drawer, he jabs a finger at the current interest rate on U.S. Treasury bills--14 percent. The budget, he notes, assumes an 11.7 percent rate.

"I don't know anyone who looks at the administration's budget assumptions and doesn't feel they have a vivid imagination."

Despite the adage that freshmen should lie low and not try to influence legislation their first term, some GOP newcomers have made a mark. Three--Claudine Schneider (R.I.), Vin Weber (Minn.) and Judd Gregg (N.H.)--ganged up against the Clinch River nuclear breeder reactor, supported by the administration and particularly by Senate Majority Leader Howard H. Baker Jr. (R-Tenn.).

Arguing fiscal conservatism more than environmental concern, they won in committee and came close on the floor.

Several freshmen are active in the "gypsy moth" caucus of moderate Republicans, including Lawrence J. DeNardis (Conn.) who is credited with putting together a compromise student loan package that softened administration cuts last year.

Others, like Rep. Frank R. Wolf (Va.), who helped push through a new policy to cut back flights at National Airport, have been active in local issues of importance to their constituents.

Idealism aside, in the back of every freshman's mind is the fact that the 1982 election is but eight months away. Thirty-three of the 53 might be considered marginal candidates: they were elected with 55 percent or less of the vote.

"We Republicans did a tremendous job in 1980 selling the idea that deficits were bad," said Hiler, a 28-year-old business school graduate who ousted Majority Leader John Brademas by painting him as "a big liberal spender."

"Now we're looking at a $50 billion deficit five years into the economic recovery. That's hard to swallow."

With a view toward reelection, many freshmen are trying to put a good face on things.

"I didn't think that it would be one year and we'd be at the end of the rainbow," said Lynn M. Martin (Ill.), whose first action in Congress was to cosponsor a resolution calling for a constitutional amendment requiring balanced budgets. "I'm not as facile with answers as I was two years ago. I'll wait longer for a balanced budget if it means reimposing inflation. Realistically, a balanced budget is not coming out of here."

Others, including Steven Gunderson (Wis.), who jokes that he represents more cows than people, have opposed the administration on farm policy and are now ready to put some distance between the president and themselves on the budget.

"If you want John Q. Citizen to support this, he's got to believe in equity. You don't increase the defense budget by 18 percent and give the White House a 17 percent staff increase, while cutting everything else."

As for Smith, he's gone so far as to write Reagan suggesting that the president take a 10 percent salary cut. "I'm not part of this old boys' club around here," he says, noting that the president has yet to take him up on the idea.