MANCHESTER, N.H. -- Local television reporter Jack Heath could hardly believe his eyes. Crossing the street and striding toward his camera position through rush-hour traffic, past a clamorous delegation from the big-time Boston stations and their state-of-the-art satellite trucks, was Sen. Joseph R. Biden Jr. (D-Del.).

It was the day after Biden quit the presidential race last September. He had just said goodbye to a group of New Hampshire supporters in a closed-door meeting. And now Boston would have to cool its heels as he talked first to Heath on the 6 o'clock news.

The Biden coup was a watershed event in the history of scrappy WMUR-TV of Manchester, and the harbinger of important changes in the mediascape of the New Hampshire primary campaign.

That mediascape has traditionally been a mix of Boston TV news, the Boston newspapers, a few small New Hampshire dailies, radio stations and low-power UHF TV stations, and -- most important -- the scaldingly right-wing Manchester Union Leader, the single statewide newspaper that quadrennially tries to break aspiring presidents with a flourish of its poison pen.

But now, for the first time during a presidential election cycle climaxing with the Feb. 16 primary, a substantial number of potential voters are turning to "New Hampshire's NewsNine," as WMUR bills itself, for an alternative view of the campaign. In the last four years the station has tripled its news staff and quadrupled its news budget. And since 1985, according to figures from the Arbitron ratings service, WMUR has doubled its New Hampshire viewership for the 6 o'clock news.

Last May, "NewsNine" made local history by pulling in enough voting-age viewers -- 47,000 -- to beat any of three Boston network affiliates in the "Manchester trading area," according to the Arbitron figures. The Manchester area comprises 15 percent of the Boston television market.

"What they have accomplished in the past eight years is something you can compare to the 'Massachusetts Miracle,' " said state Rep. Raymond C. Buckley II, the New Hampshire director of Massachusetts Gov. Michael S. Dukakis' presidential campaign.

The station has also beefed up its news programming, which in the last few months has begun to feature three half-hour shows each weekday as well as 15 minutes of morning news breaks and two half-hour Sunday panel shows. It will soon add another half-hour newscast to the two already on its weekend schedule.

"Their commitment of resources to expand news coverage is going to make it a very different player this time than last time," said New Hampshire Gov. John H. Sununu, state campaign chairman for Vice President Bush.

"I think a lot of New Hampshire opinion leaders probably watch that station more than some of the Boston stations," said Mark Longabaugh, New Hampshire coordinator for Rep. Richard A. Gephardt (D-Mo.).

Some observers have gone so far as to argue that the station, an ABC affiliate, could soon challenge the Union Leader's political primacy. The Union Leader's editor, Joseph McQuaid, pooh-poohs such talk, noting that the weekday newspaper enjoys a circulation of 70,000 while 90,000 copies of the Sunday News, the sister paper, are circulated to every corner of the state.

"Sure, the media mix has changed," McQuaid said. "The media mix has often changed in New Hampshire. But the one constant has been the dominance of the Union Leader and Sunday News."

The paper gained fame with signed front-page editorials by its late publisher, William Loeb, who liked to fling such phrases as "Skunk's skunk's skunk" to describe 1968 Democratic presidential candidate Eugene McCarthy; "Moscow Muskie" for 1972 Democratic candidate Edmund Muskie, and "Jerry the jerk" for 1976 Republican candidate President Ford -- a tradition honored today in milder form by Loeb's widow, Nackey.

"There will never be a competing statewide newspaper to the Union Leader," said Manchester lawyer John Broderick, who was a top Biden backer. "But I think Channel 9 may end up being the antidote."

"Everybody's always looking to see the Union Leader {lose} influence," Sununu said. "I see them as continuing to set the political agenda as they always have."

WMUR reaches an estimated 80 percent of New Hampshire from its transmitter on a hill west of Manchester, as well as through cable systems. This September, WMUR moved its headquarters to sleek, new offices, ending three decades of occupying a decaying Victorian mansion -- nicknamed by the staff, not necessarily with affection, the "Nightmare on Elm Street."

In the cellar lived bats, which occasionally flew into the control room, where technicians fended them off with a broom. Black and white film -- the newscast didn't go color until the mid-'70s -- was developed in fish tanks.

The station's best-known personality was for many years "Uncle Gus" Bernier -- who divided his time between hosting a kiddie show, doing the weather (dressed, in deference to the oil-company sponsor, as a gas station attendant) and occasionally reading the news, before retiring to Florida in 1981.

It seems that everyone in New Hampshire -- including most of the people currently working in campaigns -- had appeared on "The Uncle Gus Show."

"I was on 'The Uncle Gus Show' about 10 or 11 times," said Paul Young of the Kemp campaign.

"It isn't a proud period in our history," said WMUR's vice president and general manager, David Zamichow, a former New York advertising executive who orchestrated the station's transformation after arriving in 1983.

This year, he said, he is trying to boost WMUR's reputation, and "establish an identity for ourselves in political stories," by underwriting a series of local and national polls, conducted by the University of New Hampshire. Still, the station's entire news budget -- about $600,000 this year -- is roughly equivalent to the salary of a single Boston anchor.

"We're small, but we think big," news director Miles Resnick said recently over lunch. "The last election, we had 10 microwave trucks at all the campaign headquarters and 75 live shots . . . . My game is Boston. My game is beating those big giants in Boston."

Resnick, who wears screaming plaid sport jackets that match his ebullient manner, personifies the WMUR slogan, "Nine's Alive!" He leads a staff of 33, including 16 reporters and anchors -- mostly journalists in their 20s who are willing to work long hours for little pay and a chance at making it big. Typical is the lead political reporter, 24-year-old Dan Leonard, a native of Henniker, N.H., and yet another alumnus of "The Uncle Gus Show."

Since August, when he took over the job, Leonard has been closely following the comings and goings of the candidates and doing a weekly feature called "Presidential Primary Watch," in which he has examined such issues as Social Security, the environment, the value of political endorsements and the prospects for economic recession.

Campaign operatives of both parties generally give WMUR high marks for fairness, aggressiveness and a professional caliber one might see in much larger TV markets, but they occasionally note signs of political naivete. Anchor Kyle Meenan, who has since left the station for a job in Las Vegas, last month told viewers that a WMUR-sponsored poll of 410 likely voters would answer the question, "Who will New Hampshire Democrats vote for on Primary Day?" The poll, of course, revealed no such thing.

Several of the station's reporters, meanwhile, criticize Channel 9's policy of selling advertising time for political commercials during the newscasts -- something many TV stations prohibit, lest viewers confuse the commercials with the news. "We are of the opinion that viewers know the difference between a commercial and a news story," Zamichow said.

Sam Fleming, a New Hampshire-based reporter for Boston's public television station WGBH and Leonard's immediate predecessor at WMUR, suggested that the newscast relies too much on live interviews in which "a candidate gets a free two minutes to express himself in an unfiltered kind of way."

Executive news producer Gus Lalone said his main concern was "good television," as could be provided by a mediagenic candidate like Marion G. (Pat) Robertson, who recently appeared on the station twice during a two-day swing through the state.

"The guy makes for a great show," said executive news producer Lalone. "Robertson is a controversial figure. He makes people watch. He's a TV evangelist, a great speaker, and he's good television. I'd put him on five days a week if I could."

Sununu, in praising WMUR, echoed other New Hampshire officials who feel neglected by Boston television. "I think they {WMUR} understand the primary better than the Boston stations," he said.