With a new Congressional map signed into law Monday by Gov. Deval Patrick, Democrats and Republicans see a more competitive landscape for 2012 races, with pundits in both parties pointing to the districts held by U.S. Reps. Barney Frank, John Tierney and William Keating as potential nail-biters.

“I think the districts are by and large competitive, which is … good for the democracy,” Gov. Deval Patrick said minutes after he signed legislation reducing the state’s Congressional districts from 10 to 9, bolstering a majority-minority district centered on Boston creating an incumbent-free district that includes the Cape and Islands, parts of southeastern Massachusetts and portion of the South Shore.

“I think it’s a good map. It’s not a perfect map. I know that there are communities and towns that have been split,” Patrick told reporters. “Usually when they asked me about it, I say, ‘Well what town would you have split?’ I very rarely get an answer. But it’s in the nature of redistricting that there are going to be some choices that when you get down to the actual lines are delicate.”

Patrick’s hometown of Milton was divided by the map he signed over vocal objections of the community’s senator, Brian Joyce. Joyce contended that the unity of his town had been sacrificed at “the altar of political correctness,” a casualty of efforts to shore up a majority-minority voting-age district. Cambridge was also split for the first time in 70 years, according to area lawmakers who unsuccessfully sought to reunite the city.

The new maps feature 727,514 people in six districts and 727,515 in three districts, an attempt at “zero deviation” districts that forced mapmakers, mindful of lawsuits, to split not just communities but precincts as well, which means some people who live on the same street might fall in different districts. The recalibrated map sends whole communities into new Congressional districts.

Patrick also signed earlier this month a pair of maps that redraw the political boundaries for state House and Senate districts.

The once-a-decade redistricting process reflects changes in the state’s population, as determined by the 2010 U.S. Census, which showed a slow climb in the number of Massachusetts residents that lagged the rest of the nation. That forced members of the Legislature to draw up a nine-district map.

“I think that the balance that’s been struck by all three of the maps – not just the congressional but the House and Senate – has been very, very responsible,” Patrick said.

House Speaker Robert DeLeo, cognizant of the legal pitfalls that accompany redistricting, said he told his colleagues earlier this year that the stakes were high. His predecessor, Thomas Finneran, pled guilty in 2006 to an obstruction of justice charge as a result of his testimony in a redistricting lawsuit.

“When we started this session we had a little bit of a caucus, and one of the things I mentioned at that caucus was we’re going to be tackling some very difficult pieces of legislation – whether it’s … anti-human-trafficking, whether it’s gaming, whatever it may be,” he said. “But I said, how we’re perceived as a House and a Senate and as a government, a lot of that perception is going to look upon what we do with redistricting.”

“I can’t remember a piece of legislation that has received the endorsement of the Boston newspapers, newspapers from across the state, different advocacy groups from across the state, because of its openness, because of its transparency,” he said. “That’s why I have to say, of all of the accomplishments that we’ve had in this legislative session this really has to rank up there as one of the greatest accomplishments that we have to show and to prove to folks that we took a very difficult issue – we all know the changes in the Congressional districts – but we really made some changes.”

While opinions of individual members of Congress vary, incumbents all over the country are mindful of the potential ramifications for them of gridlock in Washington over job creation and budget-balancing issues, as well as polls showing historically low job approval ratings for Congress as a whole. Pundits and political operatives on both sides of the aisle see an altered landscape that could be a challenge to some incumbents.

“If there is one seat the Democrats should worry about it is the 6th Congressional District,” said Mary Anne Marsh, a Democratic strategist, referring to the northeastern district of the state occupied by Congressman Tierney of Salem. In addition a newly configured district, Tierney is facing questions about his knowledge of his wife’s role in a tax fraud scheme that netted her a 30-day jail sentence last year.

“With new swing communities, a new challenger in former Republican state Senator Richard Tisei and some lingering issues regarding his wife's legal issues, Congressman John Tierney may have the toughest fight in 2012 for re-election,” Marsh said.

Tim Buckley, Massachusetts Republican Party spokesman, generally described the Congressional map as an “incumbent protection program,” but said changes in the makeup of the districts represented by Tierney and Frank and the southern district Keating that plans to move to are positives for Republicans.

“Regardless of the shape of the jigsaw puzzle that we have here in Massachusetts, voters generally are frustrated with the gridlock in Washington D.C., and frustrated with the status quo,” he said. “For that reason, Republican challengers all stand a good shot at taking back some of these seats.”

Not so fast, countered Democratic Party Chairman John Walsh, who described the districts as “drawn fairly” but rejected the notion that Republicans would make gains in 2012.

“We have a strong, effective Democrat in each of these districts running for reelection. In the political atmosphere we’re in now, which I think is healthy, there will be some competition,” he said. “These [Republican] candidates in Massachusetts are asking voters to send John Boehner reinforcements? I don’t think that’s going to work. I think that’s going to be a very big impediment for Republican candidates in Massachusetts … But it’s worthy of a campaign, it’s worthy of a discussion and a contest. That’s how this election’s going to be fought, and I think won.”