WASHINGTON (AP) _ Are members of Congress ready to turn their backs on the massive flow of special interest money into political campaigns? A tiny, bipartisan band of senators is hoping the answer is yes.

Their target is political action committees that are playing an ever larger role in providing the cash essential to running campaigns.

Two senators have unveiled legislation to provide limited public financing of Senate campaigns while a third has introduced a bill to restrict the amount of money House and Senate candidates can accept from special interests.

All three are taking aim at the increasing role of labor, business and ideological political action committees in congressional campaigns. PACs pumped $103 million into races in 1984, an eightfold increase in 10 years, according to Common Cause, the self-described citizens' lobby.

The public financing proposal sponsored by Sens. Charles McC. Mathias, R- Md., and Paul Simon, D-Ill., would set up a voluntary income tax checkoff system similar to the one that pays for presidential campaigns.

The plan would apply only to general elections for the Senate. Left untouched are Senate primaries, all House elections and the ability of PACs to independently spend unlimited amounts for or against candidates.

''We have to take one step at a time,'' Simon said at a news conference last Thursday. ''Our present system of financing campaigns is keyed to respond to the wishes of the rich and powerful. There's no question it has an impact on the conduct of legislators and the results of the legislation.''

The Mathias-Simon plan would impose spending limits, tied to a state's population, on candidates opting to receive public money. Participating candidates would get an amount equal to the spending limit, ranging from $500,000 in the least populous states to $5.7 million in California.

If a candidate's general election opponent decided not to accept money from the public fund, the participating candidate would be able to get additional public money equal to the amount by which the opponent exceeded the state's limit.

The other bill, introduced Thursday by Sen. David Boren, D-Okla., generally would put a $100,000 limit per election cycle on the amount House candidates can receive in PAC contributions. For Senate candidates, the ceiling would be from $175,000 to $750,000, depending on the size of a state's population.

Boren's bill would also cut from $5,000 to $3,000 the amount a single PAC can contribute to a candidate and raise from $1,000 to $1,500 the amount an individual can give.

''The mushrooming growth of PACs and their influence on elections threatens the concept of grass-roots democracy,'' Boren said in a statement.

He said PACs are ''eroding the public confidence in the electoral process, increasing the danger of actual or apparent corruption of the political process, driving up the cost of campaigns and leading to increased difficulty in reaching a national consensus.''

Boren, who does not accept PAC money for his own campaigns, was joined at a news conference on Friday by Archibald Cox, the former Watergate prosecutor who now is chairman of Common Cause.

Cox called the bill an effort ''to check the torrents of special interest money that are corrupting our political system.''

Mathias and Simon said their plan was geared to take effect with the 1988 elections and that there now is enough unspent money in the presidential fund to cover the estimated $70 million to $100 million cost of financing Senate races.

Mathias, who is retiring from the Senate next year, estimated that a Senate race in Maryland in 1986 will cost a candidate $4 million, about four times what he spent in 1980.

Those figures, however, are pale when compared with the record $25 million spent in North Carolina by Senate candidates in last year's primary and general elections. With both candidates observing a limit, the Mathias-Simon plan would cap general election outlays at $3 million in North Carolina.

Common Cause said that congressional candidates had combined spending of $374 million last year, $136.9 million of it in 33 Senate contests.

Simon said all senators at least privately favor a change in an existing system that gives big contributors ''inordinate access to policymakers'' and makes ''you feel an obligation to people who contributed to your campaign.''

Mathias said the public financing bill has a ''pretty good'' chance of being sent to the floor by the Rules and Administration Committee, which he chairs. Asked about its prospects in the full Senate, he said, ''We'll see.''