House Minority Leader Nancy Pelosi, the California Democrat who served as speaker from 2007 to 2010, said Frank's ability to push through the regulatory overhaul "exemplified his time as Chairman of the Financial Services Committee during one of its most productive periods of legislating in recent memory."

President Barack Obama said of Frank that it is "only thanks to his leadership" that the law made it to Obama's desk. Dodd said in a statement that Frank was "irreplaceable."

During the 2008 financial crisis, Frank worked with House Republicans to win passage of President George W. Bush's $700 billion financial-market rescue package. Opposition in both parties created "significant difficulty" for the legislation, said lobbyist and Democratic strategist Steve Elmendorf. The bill wouldn't have passed without Frank, he said.

Frank "gave the issue great credibility on the left" by "making sure it was done right," Elmendorf said in a telephone interview.

At a press conference yesterday in Newton, Frank cited increased partisanship in Congress as a reason for his retirement. "The kind of work I felt best at is not going to be as productive for the foreseeable future," he said.

Also contributing to his decision, Frank said, was that he would have faced a demanding re-election campaign after Massachusetts, which lost one congressional seat as a result of the census, re-shaped his district.

Paul Lindsay, a spokesman for the National Republican Congressional Campaign Committee, didn't join in the praise for Frank's resume. Frank "has been responsible for much of the big government agenda that Democrats have pursued," Lindsay said.

In the runup to the financial crisis, Frank became a target of Republicans for supporting Fannie Mae and Freddie Mac, the mortgage companies that were taken into government conservatorship in 2008 after their stake in failed subprime loans pushed them to the brink of collapse. Frank defended himself yesterday, saying the Democrats weren't in the majority from 1995 through 2006 and had little power to control legislation to rein in the firms. He acknowledged that he didn't see the financial crisis coming and said he didn't become concerned about the mortgage firms until 2004.

Frank's congressional career survived a 1990 House reprimand for using his office to help a male prostitute. The House voted against more severe punishments, including expulsion, after Frank was accused of using his influence to fix parking tickets that the man had accumulated. Frank, at the time, said he "should have known better."

While Frank has spent plenty of time sparring with Wall Street over compensation, income inequality and their trading strategies, Frank Keating, the president and chief executive officer of the American Bankers Association, said the lawmaker's "depth of knowledge and willingness to be open to opposing viewpoints will be greatly missed."