At some credit unions, members filling out deposit slips are also offered a telephone to call Congress or a post-card to send lawmakers. On Capitol Hill, local bankers are appearing in force.

It is part of a massive grass-roots lobbying campaign pitting two of the country's best-monied interests in a legislative struggle. At issue is just how far credit unions can expand their services and membership."The credit union has an advantage based upon sheer numbers," said Rep. Steven LaTourette of Ohio, chief Republican sponsor of legislation that would benefit the credit unions. "Banks have an advantage in campaign contributions. I'm going to bet on the sheer numbers."

Lawmakers are debating whether to restrict booming credit union membership or subject them to the same taxes and regulations as banks.

Credit unions, which are non-profit, do not have to pay taxes on their earnings. Nor are they required to invest in low-income communities where they are located.

The issue has emerged because the Supreme Court last month ruled that corporate credit unions could not accept outside members. A bill to overturn that decision was approved Thursday on a voice vote in the House Banking Committee. It now goes to the House floor, where it has 190 co-sponsors.

The banking industry, meanwhile, is spending $1 million to bring local bankers to the capital to make a personal pitch for new limitations on credit unions. They are armed with a 13-to-1 advantage in political donations over credit unions and a 5-to-1 advantage in money spent on professional lobbyists.

For their part, credit unions are trying to mobilize their 70 million-plus members. Besides the telephones in the lobbies, some credit unions are offering pre-addressed postcards, awaiting just a personal note. Other credit unions offer postcards with pre-written messages supporting the legislation that need just a signature.

"Credit unions are really the third rail of American politics. You have so many members in them," said Rep. Chris Cannon, R-Utah, who has gotten 1,500 letters from credit union members.

That is more mail than Cannon has received on taxes, Medicaid and the balanced budget combined. He has introduced a more limited bill to allow credit unions to keep their current outside members but not allow them to accept new ones.

The bankers refuse to be outdone.

The American Bankers Association has a monthly magazine, biweekly newsletter and weekly fax report, all exhorting local bankers to contact Congress.

The Independent Bankers Association of America, the trade group for smaller banks, allocated $1 million to send bankers to Washington to meet lawmakers

"You cannot underemphasize the importance of constituents communicating with their members," said Bob Schmermund, a spokesman for America's Community Bankers, the trade group representing savings banks and savings and loan associations.

Both sides also have taken to the airwaves and newspapers. The bankers are placing advertisements in Washington-based publications and on radio stations here.

Credit unions have targeted their commercials and ads in 11 states that are home to members of the Senate and House banking committees.

The bankers' advantage is in money. Since Jan. 1, 1997, banking political action committees have contributed $5 million to federal candidates, compared with just $374,000 in donations from the credit union industry, according to the Center for Responsive Politics.

The PAC of the Independent Bankers Association of America is boosting its contributions.

"Campaign contributions are very important in an election year," said the group's executive vice president, Kenneth A. Guenther.

In addition, the bankers spent more than $5.5 million on professional lobbyists in 1997, more than four times the $1.2 million spent by credit unions, lobbying disclosure reports show.

Besides their own in-house lobbyists, the American Bankers Association has hired the heavyweight law firm of Covington & Burling. The credit unions have brought in the high-powered public relations firm of Hill and Knowlton.

The credit unions are pressing to narrow the financial gap. Since February 1997, seven new political action committees representing credit unions have registered with the Federal Election Commission.

The industry's national trade group, the Credit Union National Association, is asking every credit union member to contribute $1 to its PAC.