One of the nation's most bitter campaigns ended today with a flurry of vitriol as Gov. James B. Hunt and other Democrats struggled to avoid being buried in a Reagan avalanche that threatens to change North Carolina's political landscape.

Trailing Sen. Jesse Helms (R-N.C.) narrowly in opinion polls, Hunt criss-crossed the state today describing the country's most closely watched Senate race in apocalyptic terms. His campaign also showed a slick, 30-minute television film portraying Helms, leader of the Senate's New Right forces, as a "right-wing extremist."

Hunt told a news conference that "North Carolina should not be represented by a senator who puts his first priority on the Rev. Jerry Falwell and the Moral Majority, Nelson Bunker Hunt and a handful of Texas oil millionaires and right-wing dictators in Latin America."

Helms, visibly irritated, told reporters that Hunt's television program is a "vicious diatribe" and "a desperate attack."

"I knew the governor was willing to sink low, but I didn't think he would sink that low," Helms said. "He is desperate. He is furious. He is frightened, and he is frustrated."

Without elaborating, Helms added, "Let's talk about the homosexuals, the labor-union bosses and the crooks that support Gov. Hunt."

In terms of ideological conflict or sheer venom, few states have seen such a campaign as this one.

It has been the longest (two years), most expensive (more than $21 million) and most technologically advanced Senate campaign in history. About 7,800 television advertisements have been broadcast in the last five weeks alone.

Democratic strategists today conceded that a Reagan landslide also threatens gubernatorial nominee Rufus Edmisten, running in a race with no incumbent, and at least two Democratic congressmen, Reps. Ike Andrews and James McClure Clarke.

In no other state do Democrats have so much at stake, giving a national character to the campaign in North Carolina, where Democrats have a 3-to-1 edge in voter registration.

In a statewide Gallup Poll published Sunday, President Reagan led Democratic challenger Walter F. Mondale, 62 to 35 percent.

Mondale's tax-increase proposal, disavowed by Hunt, has been an albatross around the governor's neck. Throughout this fall, he and other Democrats have battled accusations that they are "Mondale liberals."

"It's not the coattails but the context that has caused problems," Hunt's campaign codirector, Gary Pearce, said. "Mondale's strategy has made a lot of Democrats run their campaigns focused on taxes, and that is not a good issue for Democrats."

Edmisten, who trailed Rep. James G. Martin (R-N.C.) by five percentage points in the weekend Gallup Poll, complained, "Without Reagan, I would be 15 points ahead. Mondale is killing us in this state." Helms led Hunt, 49 to 46 percent, in that poll.

"There is a fundamental rejection in North Carolina of the direction of the national Democratic Party," Hunt strategist Joe Grimsley said, estimating that Hunt loses one percentage point for every percentage point that Mondale's support dips below 40 percent.

Helms acknowledged that Reagan's popularity has helped him. But, he said today, "It sounds to me like the governor is trying to explain his defeat tomorrow."

A two-term senator, Helms has frequently tangled with the Reagan White House, the State Department and fellow GOP senators. But this fall, he has attached himself firmly to Reagan's coattails, and such prominent Republicans as Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) and Senate Finance Committee Chairman Robert J. Dole (R-Kan.) have campaigned for him.

The Reagan link is clear in Helms' final wave of commercials. One advertisement shows Reagan fondly endorsing Helms. Another shows Hunt saying, "Of course, I'm for Mondale." A third says Hunt wants to increase taxes $157 a month for everyone.

The Helms-Hunt battle invites superlatives and has been described here as Armageddon, a holy war, a crusade, a fight between good and evil and a battle between the Old South and the New South.

Helms, 63, is an unabashed conservative, almost a cult figure to many in the national conservative movement. Although he heads the Senate Agriculture Committee, he is best known for championing such New-Right causes as banning abortion and restoring prayer in public schools.

His political base is the National Congressional Club, a political action committee established by his allies to raise millions of dollars through direct mail and funnel them into his campaigns and those of other conservatives.

Part of Helms' appeal involves race. His standing among whites, for example, shot up in polls after he led a filibuster against a bill establishing a national holiday on the birthday of the late Rev. Martin Luther King Jr.

Helms' appeal is much broader, however. A former television commentator, he is a skilled orator and a jocular, grandfatherly figure on the stump whose maverick ways attract some who disagree with him on specific issues.

Hunt, 47, is a consensus politician, twice elected governor with more than 60 percent of the vote and a moderate who supports the B1 bomber, the MX missile and the balanced-budget amendment. He has built a national reputation for bringing new industry to North Carolina and improving its educational system.

He also is a skilled political organizer who has created a powerful state political machine.

Despite 20 months of television commercials, many of them brutally negative, the contest has been surprisingly close for months. Helms' three-percentage-point Gallup lead is one point less than his lead last May.

Officials of both campaigns have said they realize that their negative ads have polarized and offended many voters. Hunt has apologized for this and pledged, if elected, to try placing limits on television advertising and fund-raising. Helms' campaign has raised more than $13 million and Hunt has raised more than $8 million.

Helms, whose private polls give him a five-point lead, has tried to be uncontroversial in the closing days of the campaign.

Hunt has launched several bitter attacks in hopes of gaining ground. His ads have accused Helms of opposing Social Security and veterans benefits and supporting an anti-abortion bill that Hunt claims would make intrauterine devices and other birth-control measures illegal.

He has compared Helms to former president Richard M. Nixon, accusing him of "covering up" a Federal Election Commission investigation of the National Congressional Club. He has charged that "Republican-appointed U.S. attorneys have begun the most shameless effort I've ever seen to prevent Democrats from voting" in the state.

The centerpiece of Hunt's final push is a 30-minute film broadcast during prime time tonight and Sunday. Narrated by actor Hal Linden, it was presented like a network documentary.

It portrayed Helms as leader of a "tight, ideological, right-wing political network." It said he has interlocking ties with Falwell, founder of the Moral Majority; Phyllis Schlafly, head of the conservative Eagle Forum and a leader of opposition to the Equal Rights Amendment; the Rev. Sun Myung Moon, head of the Unification Church, and "right-wing political and military dictators around the world."