The process of presidential campaigning has been so corrupted by "media events" -- posing the candidates in settings that convey a message on a TV tube without verbal content -- that there is a tendency to view all visual spectacles as essentially phony.

At a Common Cause forum the other day, Linda Wertheimer of National Public Radio was ridiculing the "Italian market syndrome" that seems to send every candidate who comes to Philadelphia out shopping for saussage and eggplant as a shortcut to the ethnic vote.

Next Monday, Ronald Reagan and George Bush will take part in what looks like an equally phony "media event." They are scheduled to meet on the steps of the Capitol with the Republican congressional leaders, members of Congress and a sizable number of GOP candidates from the House and Senate.

There, according to plans, they will announce a list of specific actions that they jointly pledge to take in 1981, if Reagan is elected with a Republican Congress.

Since the odds are against the Republicans' overturning the 26-year-old Democratic majorities in both the House and Senate this November, the "contract" Reagan and the Republicans are offering can be seen as a cheap promise to make -- just another "media event" on the candidate's schedule.

But the ceremony has substantive significance, at least in the minds of the junior House Republicans who concocted the notion and sold it to a somewhat reluctant Reagan campaign. It represents a serious and healthy departure from the norms of contemporary presidential campaigning.

For the last quarter-century, most of the presidential nominees of both parties have run for office as it the presidency were the only job on the ballot and they were the only candidates.

Losers like Barry Goldwater and Hubert Humphrey might proclaim their party labels. But for the most part, the successful candidates of both parties from Eisenhower through Carter have told the American people that a change of governmental direction could be achieved by changing the occupant of the White House.

That proposition has been proven false. The inertial forces in the government of the United States -- the network of relationships linking the bureaucracy, the interest groups and the congressional subcommittees and their staffs -- are demonstrably too powerful to be turned around by any one man.

What the Republicans are attempting to say with their Capitol steps theatrical is that Americans who want to change directions have to change control of the whole government. They have to reverse the majorities in Congress as well as turn out the incumbent from the White House.

It is proposition that offers great potential dividends for the congressional Republicans. Too often their candidates have found themselves competing with Democratic incumbents who are as vociferous as the challengers in denouncing the "mess in Washington."

The Republicans hope, by the Monday spectacular, to drive home the point that the Democratic Congress is as much responsible for the record of the last four years as is the Democratic president -- and that individual Democratic senators and representatives must be held to account for their party's record.

But it is a strategy with obvious risks for Reagan. It will be fascinating to see how far he really goes in expounding the message the sponsors hope to communicate.

From Eisenhower on, Republican presidential candidates have known that they have to run well ahead of their party to have a chance of winning. Most often, that has meant running far away from their party. Ever since the Democrats took over Congress in Eisenhower's second year, Republican presidents and presidential candidates have been content to seek accommodation, not revolution, on Capitol Hill.

In Reagan's case, there is a special risk in the Monday event. His own strategists say that most voters believe that Reagan is a stronger executive than Carter, a man more likely to get things done. But, these strategists concede, there are still grave reservations about the direction in which Reagan would move the country.

Many voters -- women in particular -- are nervous about Reagan's talk about a bigger, more bristling defense, a tougher line toward foreign governments and a greater reliance on private industry to furnish the jobs and energy the country needs.

Many of those voters who are fed up with Carter but nervous about Reagan would like to hedge their bets by keeping the Democrats in control of Congress -- a sort of check-and-balance strategy -- as they did when they elected Eisenhower and Nixon three times with Democratic Congresses.

The implicit message of Monday's ceremony is that there can be only one government in Washington at a time and that if voters want Reagan to lead it effectively, they have to go all the way with the GOP.

That is an honest statement, and it is as commendable for the Republicans to dramatize it as it is risky.