The Senate's television debut yesterday marked the end of an almost 30-year cycle during which the two chambers of Congress have by turns gradually and warily tested their ability to function while television came to dominate national political discourse.

Although it lagged seven years behind the House in opening floor proceedings to television cameras, the Senate pioneered in introducing Congress to the television age.

In 1947, the first telecast of a congressional proceeding was of then-Secretary of State George C. Marshall telling a Senate committee about his plan for reviving war-ravaged Europe.

For the next 24 years, the Senate had congressional television to itself. In the 1950s, televised committee hearings helped establish the national reputations of men as diverse as Joseph R. McCarthy of Wisconsin, Estes Kefauver of Tennessee and John F. Kennedy of Massachusetts. Not until 1971 did the House change its rules to allow televising of committee hearings.

On March 19, 1979, the House chamber was opened to television cameras, and floor proceedings were beamed nationally over the Cable Satellite Public Affairs Network (C-Span).

From that moment, in the view of several observers, it was all but inevitable that the Senate would eventually follow.

"The Senate had no choice" but to allow television cameras, Eddie Mahe, a Republican political consultant, said yesterday. "The House was eclipsing the Senate because you could see the House doing things and you never knew what the Senate was doing."

Michael J. Robinson, director of the Media Analysis Project at George Washington University, agreed that the Senate was "terrified" at the thought of the House becoming the more prominent of the two because of television.

Based on his studies, however, Robinson said neither this fear nor concern that television would have a major impact on House proceedings was well founded.

"There has been some incremental change in the way the House does business and very marginal change in terms of public perception of the House because of television," Robinson said.

He said the changes included a slight increase in partisanship and ideological rhetoric, a slight decline in House members' willingness to follow party leaders' dictates.

Robinson also argued that, because House members can now follow floor debates from their offices, they are generally better-informed, an observation seconded by a longtime House employe, who asked not to be identified.

"We are getting a much more intelligent vote," the employe said. "They come to the floor knowing what the vote is about, and you rarely see a member walk in and ask an employe what the vote is."

Television has clearly had an impact on the House party leadership. Thanks in part to C-Span, Thomas P. (Tip) O'Neill Jr. (D-Mass.) is almost certainly the most widely known and visible speaker of the House in history.

"The job has changed dramatically to become much more that of a party spokesman," said Kirk O'Donnell, a former top aide to O'Neill. However, the national prominence of a Democratic speaker is also likely to decline if Democrats gain control of the Senate and the White House.

On the Republican side, C-Span helped give rise to the Conservative Opportunity Society, a group of young GOP lawmakers who played to the television audience in long, often ideological speeches during "special orders," a time reserved for speech-making after close of legislative business.

This, in turn, has probably pushed the established House Republican leadership into a more partisan posture.

To counter what he considered their partisan antics, in May 1984 O'Neill ordered cameras occasionally to pan the usually empty House chamber as these speeches were given. Whether this bit of television direction had its desired effect, it was an example of what is widely seen as the House's ability to adapt successfully to the television age.

"The real fear was that guys would grandstand," said Gary Hymel, O'Neill's administrative assistant when cameras appeared.

"The answer then was that it would be self-policing, that other members would put a stop to it. In general, I think that is what's happened. Television looks over the shoulder of the House as it does its work. It doesn't interfere with the process."