Story highlights Frank says his new district boundaries contributed to his decision to retire

Frank, a Democrat, was first elected to the House from Massachusetts in 1980

A prominent liberal, he co-authored the Dodd-Frank financial reform bill

Frank, an openly gay member of Congress, was reprimanded by the House in 1990

U.S. Rep. Barney Frank, a prominent 16-term liberal Democrat from Massachusetts and arch-enemy of political conservatives nationwide, announced Monday that he does not intend to seek re-election in 2012.

Frank, 71, said his decision to retire from Congress was prompted partly by changes made to the boundaries of his U.S. House district. As part of Massachusetts' recently concluded redistricting process, Frank's 4th Congressional District will lose the heavily Democratic blue-collar port city of New Bedford while gaining several smaller, more conservative towns.

"I will miss this job, (but) the district is very substantially changed," with roughly 325,000 new constituents, Frank told reporters. The veteran congressman said he was planning to retire after 2014 regardless, but said he didn't "want to be torn" next year between the need to serve his existing constituents, reach out to new district residents and protect his signature Dodd-Frank financial regulatory reform law.

President Barack Obama issued a statement praising Frank's public service, calling the congressman a "fierce advocate for the people of Massachusetts and Americans everywhere who needed a voice."

While Massachusetts' entire House delegation is Democratic, local Republicans insist Frank's retirement will put the reconfigured district in play.

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"It is clear that Congressman Frank was not looking forward to another hard fought campaign after losing his gerrymandered district and spending nearly every penny he had in 2010," Massachusetts Republican Party Executive Director Nate Little said in a written statement.

"Republicans were already gearing up for a strong race and Frank's sudden retirement injects added optimism and excitement into the election."

Frank, first elected to the U.S. House of Representatives in 1980, is the top Democrat on the powerful House Financial Services Committee. The controversial 2010 Dodd-Frank measure, designed to rein in Wall Street excesses after the 2008 financial collapse, passed the House without any GOP support.

Frank made headlines earlier in his career by becoming one of the first openly gay members of Congress. He was formally reprimanded by the House in 1990 for allegations relating to his association with a male prostitute.

Launching his career as an aide to Boston Mayor Kevin White in the late 1960s, Frank quickly became known for an acidic political wit.

"One of the advantages to me of not running for office is I don't even have to pretend to try to be nice to people I don't like," Frank joked with reporters Monday. "Some of you may not think I've been good at it, but I've been trying."

Frank's current district -- which extends from the affluent, liberal Boston suburbs of Newton and Brookline to the cities of New Bedford and Fall River -- is considered safe Democratic political terrain. Frank did, however, receive an unusually strong challenge from Republican Sean Bielat in 2010.

Frank ultimately defeated Bielat, 54% to 43%.