Senators who say the current method of financing congressional campaigns amounts to a national scandal pressed yesterday for an overhaul of election finance laws, but a day of hearings on the issue illustrated how complex and multi-faceted their movement is.

The testimony also revealed skepticism that campaign finance revisions would accomplish anything except create new problems that in turn would have to be reformed.

Sen. Charles McC. Mathias Jr. (R-Md.), chairman of the Senate Rules Committee, called for public financing of congressional elections as a way to drive out "corrupt money and excessive money. . . .

"I hope we will not wait for a [Watergate-type] scandal to arouse us to action," he said, promising to introduce a public financing bill shortly.

Mathias drew considerable oratorical backing from a handful of other senators who suggested the scandal has already unfolded.

"The current system of funding congressional elections is a national scandal," said Sen. Thomas F. Eagleton (D-Mo.). "It virtually forces members of Congress to go around hat in hand, begging for money from Washington-based special interests, political action committees [PACs] whose sole purpose for existing is to seek a quid pro quo."

But there was no consensus on how to achieve changes in the system.

Some said the most important thrust of any new bill should be to curb the power of the PACs, which accounted for about 27 percent of all congressional funds raised last year, up from 14 percent 10 years earlier.

Some wanted to reduce the role of so-called independent expenditure groups; some wanted to strengthen the role of parties; some to diminish the advantage of personal wealth; some to raise limits on individual contributions; some to provide public financing in the form of funding floors rather than ceilings.

Others, including a panel of election finance specialists, took a dim view of the ability of reformers to escape the law of unintended consequences.

"I have developed a congenital feeling that election reforms usually result in exactly the opposite effect of what was intended," Richard Scammon, director of the Elections Research Center, told the panel.

The only change he endorsed was lifting the ceilings on what parties could contribute directly to their candidates. This is a proposal that many Democrats oppose, since their national party fund-raising committees, the Democratic National Committee and the House and Senate campaign commitees, raise only about one-tenth of what their GOP counterparts do.

As for two election finance phenomena that have raised the hackles of many--negative campaigns waged by independent, and unaccountable, groups, and lavish campaigns self-financed by multimillionaire candidates--Scammon suggested the most reliable mechanism was "the common sense of the voter." He noted that both groups fared badly in 1982.

Amidst all the proposals and perspectives, the nearest thing to a consensus approach yesterday was the "Wisconsin Plan," which is based on a system in effect in that state. It provides for partial public financing that provides matching public funds, up to a limit, to candidates who raise money from small, individual donors and places a spending limit on them.

If a candidate chooses not to accept the funds and the spending limits, his opponent receives a two-for-one match rather than a one-for-one, and is freed from the spending limit.