THE FIRST THING Rep. Jim Coyne does at his Capitol Hill office each morning is read his computer. The Pennsylvania Republican has set up an "electronic mailbox" for messages from constituents and others who have their own computers.

Coyne's flickering screen is a sign that the notorious "communications revolution" is about to hit politics. A wave of new technology -- cable TV, satellite-to-home broadcasting, video recorders, personal computers, electronic publishing -- will transform campaigning, political organizing, news coverage, lobbying and voting, much as television transformed politics two decades ago.

The new changes may make campaigning less costly and bring decision-making closer to the people. Unfortunately, they may also further fragment our politics, shift more power to special interests and weaken the glue that holds our system together. We had best start thinking now about how we want politics to work in this new era, before events overtake and control us once more.

Start with the way the new technology, combined with deregulation, is creating a flood of new TV channels. A quarter of U.S. households now subscribe to cable TV; by 1990, the portion should exceed 50 percent. All the new systems have at least 32 channels, and the frantic bidding war for franchises is driving cable companies to promise as many as 200 channels in some cities.

The number of regular radio and TV stations on the air has doubled since 1960. The FCC is about to award hundreds of new "low power television" licenses, and direct broadcast satellites may be operating by 1986, sending as many as 20 TV channels directly from space to small rooftop receivers.

This wave of outlets is creating the economic base for "narrowcasting." The big three networks will survive and will continue to aim at mass audiences, but dozens of new services will spring up for narrow audiences. Already, the new economics has spawned networks dedicated to news, sports, weather, movies, culture, health, Hispanics, Jews, blacks, the elderly and the young.

Until now, politicians used TV to send short messages to large audiences. The new TV will mean longer messages for smaller audiences. When we watch the narrowcasting networks, we may see campaign ads and news programs showing candidates advocating bilingual education on Spanish channels, defending Social Security on channels aimed at the elderly, or playing football on sports channels. Politicians will find the all-news channels particularly fertile ground -- viewers with enough appetite for news to watch it continuously will be good prospects to contribute, volunteer and vote.

The greatest impact may be on congressional and local campaigns. A candidate running in Lansing, Mich., for example, has to pay at least $500 for a 60-second ad on a regular TV station, and most of that money is wasted because the station covers half the state. The same commercial on the local cable system costs $30 and reaches just Lansing residents. Ads are new to cable, but they will be universal in a few years.

Cable even offers free time. Most cable systems have "public access channels," which are available to anyone who wants to use them, first-come, first-served. Few access channels have regular audiences, but they are ideal for a campaign manager to brief volunteers or a political party to run a weekly talk show for its activists.

TV news itself is aready changing. In Reading, Pa., the cable system provides live coverage of city council meetings -- and has altered Reading politics. The shows helped the current mayor, Karen Miller, attract a following, beat a political machine and win her seat. "People definitely are watching us," she says.

In Madison, Wis., another pioneer in local cable coverage, city councilmen accustomed to anonymity now are treated like TV personalities -- strangers stop them in the street to praise or revile their performances.

Most new cable systems will dedicate a channel to this kind of programming, and several states are talking about letting cameras into the legislatures. A cable network has carried the U.S. House of Representatives live for the past year, and the Senate is of course debating whether to do likewise. The audiences may be small compared to "Dallas," but they are huge compared to the numbers who show up at city council meetings or House debates.

These channels are bringing events directly to people, without editing or interpretation, but electronic journalism also is growing. Two 24-hour cable news networks are on the air, and two more will start this year. In Washington and many other cities, newspapers are teaming up with cable systems to produce local news channels. These services will give us more in-depth reporting and more of what television does best -- live coverage of breaking stories. Together with the government channels, they will make politics more accessible and understandable, and that may get more people involved.

Unfortunately, though, other people may end up knowing less. Most Americans get their news from TV, and traditional broadcast news programs, superficial though they are, provide a homogenous information base.

In the new media, by contrast, some channels will offer only news about their particular themes, and some will provide no news at all. Former CBS president Richard Salant fears that "instead of a common data base, we'll have smaller and smaller groups knowing more and more about less and less."

Next, the computers. They will be changing the lives of the list-makers and envelope stuffers who are the indispensable foot soldiers of campaigns. In the last two years, computers have become cheap enough to let most campaigns automate their paperwork. In the 1982 election, the most prized volunteers will be those with personal computers.

Computers will also play a role in voter contact. A few campaigns already have used automatic dialing machines to call hundreds of people an hour and play a tape of the candidate urging them to vote. The next step will be voice recognition machines that "understand" what the person at the other end is saying. Several companies have prototypes that can handle callers' airline reservations with startling accuracy. By the 1990s we may see electronic canvassing, once people get used to talking with machines.

Computers, moreover, will help "target" messages and money to particular groups. The Republican National Committee is planning to give local candidates access to the its national data banks, to provide instant information and analysis in the heat of campaigns.

The new technologies will do even more for interest groups. The Chamber of Commerce is about to launch its own TV network. BizNet will use a satellite to broadcast six hours a day of business news, interviews and, of course, lobbying messages to receivers at corporate headquarters around the country. The Chamber has spent $5 million on studios and will spend several millions more each year to run the operation.

BizNet is pioneering a migration that will sweep through political organizations -- the shift from high-cost mail to electronics. For the price of a fund-raising mailing, a group can now reach more than a million people with 100 two-minute ads on a cable network. For the price of a newsletter, a group can produce up to 10 one-hour TV shows, and some new networks are so hungry for programming that they will give away air time.

This, plus the emotional impact of the visual, is why Richard Viguerie, leading fundraiser for conservative causes, says that "cable television will be to the politics of the 1980s what direct mail was to the 1970s."

Only one group has fully exploited the new media so far -- religious denominations that acquired UHF TV stations and created satellite-fed networks reaching millions. Most political organizations are hanging back, but a few are moving. The United Auto Workers, for example, has applied for 24 low-power stations to start its own TV network.

By the end of the decade, trade associations, corporations, unions and political parties will be turning out oceans of videotape. This "electronic direct mail" will be a key tool of political organizing.

Still another potent tool: the video teleconference. Last December, for example, Vice President Bush had promised to speak to GOP contributors in California, but he could not spare the time for the trip. Instead, he went to a studio a mile from the White House, talked by satellite, and answered questions from the audience.

Similarly, the National Education Association last year wanted to mobilize 1,000 organizers across the country for a letter-writing campaign on a budget issue. Instead of flying everyone to Washington, it brought them to 49 sites around the country and plotted strategy by satellite. The conference saved $250,000 in air fares and hotel bills.

By 1990, similar electronic meetings between congressmen and constituents will be a routine part of lobbying. Electronic meetings will not have quite the impact of face-to-face contact, but they will get the message across.

The most dramatic changes of all may be in polling. The 1980 Reagan-Carter debate gave us the first glimpse of what may be in store. After the debate, the ABC network asked viewers to call a special phone number and record their preference. Within hours, an AT&T computer tallied millions of votes and pronounced Reagan the winner.

A two-way cable TV system in Columbus, Ohio, called QUBE illustrates the next stage. Subscribers are given a small box with several buttons, connected to the TV. A TV announcer asks a question and gives the audience four choices; home viewers push the button for the answer they like. Within seconds, the results flash on the screen.

This year, cable companies will install two- way gear in half a dozen new cities. Other companies are developing two-way systems that use the telephone network. By 1990, as much as a quarter of the population may be using these so-called "videotex" systems to get information, bank and shop from home. All those people will be able to participate in electronic polls.

The new technology may even be used for elections. San Diego showed what can happen when it ran a bond referendum by mail last year and the turnout doubled. Registrar of Voters Rudy Ortiz commented, "In the future, elections may be done by telephonics. We may just be showing the way."

QUBE subscribers apparently like talking back to their TVs. Larry Wangberg, the cable executive who oversees the project, says it is "boosting the citizen interest-level" in politics. Alvin Toffler's book about the information age, "The Third Wave," predicts that in time this technology will "combine direct citizen participation with 'representation' into a new system of semi-direct democracy."

But electronic polling also poses the new technology's clearest dangers. First, the results are skewed. These polls count only those who have terminals and who bother to respond -- hardly a cross-section. Moreover, existing two-way systems cannot tell who is pushing the buttons; many "voters" could be 4-year-olds.

Second, these polls measure people's instant, emotional reactions. They are powerful because they involves many more people than the old-fashioned Gallup and Harris surveys, and they get answers a week faster. But they deny people the chance to think about issues and omit follow-up questions that measure how deeply people feel. One shudders at the idea of instant referenda on the Panama Canal treaty or proposed responses to the Iran hostage seizure.

Finally, electronic voting offers a perilously convenient way for politicians to bias results or escape hard decisions. "Any fool knows you can control the outcome by how you ask the questions," warns Mayor Miller. "You could have some pretty atrocious acts justified by this."

These perils are in addition to arthe threat from the new media: further dilution of the fragile glue of the political parties and of public identification with broad ideas. The art of saying different things to different people is hardly new, but the advent of narrowcasting and electronic direct mail will make it easier to do and harder to catch.

The new technology also will touch off another scramble for money to buy teleconferencing studios, satellite transmitters and fancy computers. Only the well-heeled will have the funds to buy all the new machines and produce enough programs to fill the channels.

On the other hand, the new technology should reduce the sense of distance from government that many feel, and live TV coverage may make politicans more responsive to the general public. Low-cost cable ads, free access channels and cheap computers should also help struggling causes buy TV time and use time-saving automation. The parties themselves can use the technology to raise money and organize supporters.

Some of the effects on the balance of political power will depend on how the new media are regulated. The Communications Act requries TV and radio broadcasters to sell time to candidates at minimum rates, to treat all candidates equally and to provide balanced coverage of controversial issues, but the application of the rules to cable and satellite-to- home broadcasting is foggy. Congress and the FCC are also beginning to debate whether concentration of ownership in the new media should be limited and whether access should be guaranteed.

In 1952, few politicians paid much attention when TV cameras were trundled into the national party conventions. This time politicians and the rest of us had better take note and help shape this new world.