he PTA program chairman was a little stunned to see the tanned, husky man walk into her candidates' night.

With the World Series on, only 42 people had showed up to hear a few local school board candidates.

She certainly did not expect a U.S. senator.

But in his race for a fifth term in the Senate, Howard W. Cannon at age 70 has just survived the scare of his life, a primary in which he won with only 49.7 percent of the vote and lost every county in the state but two.

The veteran lawmaker appears unlikely to cut down his heavy campaign schedule until every voter has been approached.

"I am seventh in seniority in the Senate, I'm the Democratic Party's senior member on the Rules Committee," he reminded the small audience, restating for the ten-thousandth time his campaign theme: Howard Cannon is too important a man to lose in a state as dependent on federal government and tourist money as Nevada.

He enumerated the industries he helped deregulate as Commerce Committee member and chairman: "the airlines, . . . the trucking industry, . . . the rail industry, . . . the telecommunications industry."

The next day, in a ramshackle headquarters on the other side of this neon-lit desert city, a small, slim man with a tan rivaling Cannon's was turning the senator's argument upside down.

"Cannon is the Washington candidate. I'm the Nevada candidate," said Chic Hecht, the 53-year-old clothing store owner and former state senator who is the Republican nominee.

"Cannon," Hecht declared, "is the end of an era, the era of George McGovern, the era of Hubert Humphrey, the era of Tip O'Neill, the era of Lyndon Johnson, everything going back to Washington, let Washington take care of all the problems and tax the people to build a bigger and better Washington."

Hecht got into his primary so late and has been campaigning in such a low-key way that Cannon aides sometimes call him "the invisible man."

But he still poses a threat, particularly after the bruised feelings left by Cannon's primary victory over popular Rep. Jim Santini, who won 45.5 percent of the vote.

According to Cannon press secretary Mike Vernetti, a Cannon poll taken shortly after the primary showed the senator leading his Republican opponent 50 to 34 percent. A private poll recently cited by former Democratic governor Mike O'Callaghan, now a Las Vegas Sun columnist, showed Cannon leading 52 to 36 percent.

But Vince Breglio, executive director of the National Republican Senatorial Committee, said Hecht has erased what was once a 16-point deficit to trail Cannon in a mid-October Republican poll only 50 to 46 percent, with 4 percent undecided. Said Breglio of Hecht, who was far less well known than Cannon, "He came out of a crowded Republican field like a rock from a slingshot."

Even before Hecht won the primary, he had the blessing of former Reagan aide Lyn Nofziger as the Republican with the best chance to beat Cannon. His advertisements have emphasized his service as state senate majority leader, his support of Sen. Paul Laxalt when Laxalt was a popular governor, his advocacy of the death penalty and his close adherence to the federalist philosophy of Ronald Reagan, who has been here to campaign for him.

Despite the fact that a group of Teamster officials are now on trial in Chicago for attempting to bribe Cannon in a case where Cannon's own innocence was once in doubt, Hecht has avoided any personal attack on his opponent.

"Integrity is not an issue," Hecht says. Cannon in turn has referred to Hecht as "a nice fellow" and has simply discussed his own record.

The campaign has been so gentlemanly that Cannon aides who lived through the venomous Santini fight are left slightly dizzy.

"We had an incredible primary," said Vernetti. "The intensity level was so high. It was trench warfare every day with a new Santini charge and our countercharge."

Advisers to both Cannon and Hecht argue that Santini, a more conservative Democrat than Cannon, lost because Cannon was able to make an issue of an anti-Cannon campaign funded by the Virginia-based National Conservative Political Action Committee. Hecht wrote NCPAC officials a letter shortly after the primary asking them to stay out of the state, and so far they have appeared to comply.

Hecht spent $365,000 in his primary and expects to spend no more than $450,000 in the race against Cannon. Cannon plans to spend no more than $500,000 in the general election. Santini has returned as a Cannon booster, appearing at fund-raisers and signing a pro-Cannon letter to be sent to Democrats throughout the state. "He's proved to be a gentleman," said Cannon, who argues that all the primary wounds have healed.

Hecht said he doesn't believe it. His optimism is inspired by a long history of unusual political turns in a state loaded with conservative Democrats.

"A lot of people tell me they voted for Cannon because they thought he would be easier for me to beat," Hecht said. "When you have a man who has been a top Democrat, in the U.S. Senate for 24 years, and he only gets 50 percent of the Democratic primary vote, he is in trouble."