Ronald Reagan is an "air hog" who has abused the presidential privilege of gaining direct access to the American people through television, according to House Democratic leaders. They will make that charge when they release a 133-page report they commissioned on Reagan and the networks.

The report considers the possibility that Reagan's dominance of the airwaves may have created "a dangerous imbalance of power" between the executive and legislative branches.

Speaker of the House Thomas P. (Tip) O'Neill Jr., who will make the nonpartisan Congressional Research Service report public, thinks the networks, especially CBS, have failed repeatedly to provide equal access for opposition views following Reagan's addresses to the nation, speeches that have been designed to shape public opinion on issues before Congress.

"The Mondale-Reagan debate this Sunday will be the first time the American people will have an opportunity to see the administration and the congressional opposition address the American people on equal terms," Christopher J. Matthews, an O'Neill aide, said yesterday. "For four years the president has been able to protect himself from direct analysis by the other side. Too often, the Great Communicator has been the only communicator. He has been visible without being vulnerable."

Today's announcement and the release of the report signal a new phase for the Democrats and their often wildly disorganized four-year struggle with The Ronald Reagan Show, one of the few inarguable smasheroos of recent TV times.

All presidents in the age of television have enjoyed the advantage of access to the country via the networks, usually whenever they wanted it. So far during his presidency, Reagan has made 15 requests for air time on all three networks for "addresses to the nation" and has been turned down only once, by one network (ABC did not carry his October 1982 "stay-the-course" address on the economy). O'Neill believes the report shows that Reagan has abused the privilege, that the public has been bombarded with the Reagan view and has received insufficient exposure to the opposition's positions.

Of course, the Democrats might not be screaming at all if not for the fact that Reagan has proven himself a masterful television performer, as comfortingly grandfatherly as Walter Cronkite and as popular as Uncle Miltie (Milton Berle was once known as "Mr. Television"; Reagan deserves the title now). The report takes note of "Reagan's persuasiveness as a television communicator." Matthews says, "He's very deft at this. He's not been boring on the air. But we'd argue that it's as much electrons as eloquence -- that he's persuasive because he gets so much unchallenged air time."

The great advantage Reagan enjoys is the three-network whammy, what Matthews calls a "roadblock." When Reagan speaks on all three networks at once, he is making it very difficult for viewers to avoid him, but the Democrats rarely enjoy this advantage when they finally get air time to make their responses.

The report cites the estimate of NBC News executive (and former CBS News president) Richard S. Salant that a three-network hookup "results in an audience about five times larger than such an appearance on a single network" and that due to "the principle of no-escape," a program on three networks at once reaches a much larger audience than do three separate telecasts seen at different times on each network.

Thus the Democrats complain that while they may get as much air time to answer the president as Republicans got during the Carter administration, it is separate and unequal because not only do they not enjoy the three-network advantage, but their presentations are relegated to less advantageous viewing hours than Reagan's. Of course the Republicans had the same problem during the Carter years, but Carter was considered such a dud on television that nobody raised much fuss. If only Reagan weren't such a darned old whiz . . .

According to Matthews, in nearly four years of pink-cheeked ReagaVision, during which there were, by the Democrats' count, some 36 Reagan broadcasts on controversial issues (excluding actual news events), the Democrats got a total of 19 minutes of direct rebuttal time. Then-Rep. Richard Bolling had eight minutes to reply to a 1982 "budget summit" talk and Sen. Christopher Dodd (D-Conn.) took 11 minutes to respond to a 1983 Reagan speech on Latin America. Unfortunately, Dodd's response inspired almost as much dissension among the Democrats as Reagan's speech did. The party has often lacked a galvanizing, unifying spokesman.

And television naturally favors the presidency because the same person is always the president. He's clearly identifiable. He's the star. The Democrats have had difficulty arriving at spokesmen acceptable throughout the party. The leadership knows that some of the younger, leaner Democrats make much better television impressions, but the craggy old veterans think spokesmanship should be a privilege that comes with seniority.

Reagan proved his video prowess early in his administration. In the spring of 1981 he bounced onto the airwaves with his "Father-Knows-Best" budget lecture and, urging viewers to write their congressmen in support of his budget resolution, generated the largest volume of mail ever received by Congress in one day: 1.25 million pieces on May 4, 1981. On May 7, the Reagan budget was passed, as if by television referendum.

Most of those letters were written before the Democrats had the opportunity to present the opposing view in separate broadcasts on each network.

"Among the commercial television networks, the main offender in the eyes of the Democratic opposition in not airing timely reply broadcasts was CBS," the report notes. "They do it all the time," says Matthews. "NBC and ABC have tried harder to let us respond coherently, but CBS is the toughest nut to crack. They put together their own Friday night specials to air at 10:30. They pick the cast, they pick the format, they pick the time. There is no coherence, no chance for a game plan. Then they say they have 'given time to other views.' It amounts to purely technical compliance with the Fairness Doctrine.

"CBS insists on defining what 'the opposition' is," Matthews says. "They have repeatedly given us a purely pro forma response opportunity, a 10:30 Saturday night burial job. You can't debate somebody opposite 'The Love Boat' on Saturday night when he spoke at 8 o'clock Wednesday night."

CBS News president Edward M. Joyce said yesterday from New York that the network has been hearing this kind of criticism from whichever party was out of power since the mid-'70s, and that CBS News policy is that "whenever the president speaks on matters of major policy where there is some area of disagreement, we provide for a broadcast of other viewpoints. We determine the length, the time and the participants and we try to schedule it as soon as practicable, but generally no later than a week after the president speaks."

Joyce compared the Democratic protest to the pressure applied by the Republicans last summer to get the networks to air an 18-minute film extolling the saintliness of President Reagan. "Both parties have made attempts this year to decide the content of our news coverage," Joyce said. The CBS position regarding rebuttals to presidential addresses, said Joyce, is that the definition of "the opposition" should not be limited to "the out-of-office party" but should include other voices as well. Matthews says this stance is ridiculous, especially on "binary" matters like legislation before Congress, when a congressman has to decide, no matter how many different views there may be, to vote either yea or nay.

The report states that the Reagan broadcasts have been "remarkable" for their "apparent importance to him in influencing legislation pending in Congress. The timing and theme of presidential forums receiving live television network coverage in certain instances appear to have had an unmistakable impact on measures being considered by Congress. On three occasions, the simultaneous access to the three commercial television networks which the president used for addresses on his economic program was followed days later by passage in the House of Representatives of Reagan-backed budget or tax measures over the opposition of House Democratic leadership.

"In each instance, the Democratic opposition failed to gain simultaneous access to the three networks for a rejoinder to the president. As a result, significantly smaller network audiences overall were probably reached by the rebuttals than by President Reagan."

The report does not come to the conclusion that the presidential advantage, as cannily exercised by Reagan, could be disruptive to the whole checks-and-balances system; it merely raises the possibility. "Such an imbalance, it is argued, creates an imbalance of power between the presidency and Congress, especially when the two institutions come into conflict over a policy matter and only the president is allowed special access to present his case to the public," the report says.

Whether the Democrats think the imbalance really is "dangerous" to the republic is probably beside the point right now. What they know for sure is that is has been dangerous to them.