Groton - Throughout most of Chris Murphy's career in politics, his name barely appeared in print without the word "precocious."

He was class president at Wethersfield High and a teenage volunteer for town council races. At 22, after graduating from Williams College, he managed the 1996 congressional campaign of Democrat Charlotte Koskoff when she nearly upset the 5th District's longtime incumbent, Republican Nancy Johnson.

At 25, Murphy was elected as a Southington Democrat to the state House of Representatives; four years later he joined the state Senate. In 2006, at age 33, he took on Johnson and defeated her by 13 percentage points. She had been the longest-serving member of Congress in Connecticut history.

In this year's race for U.S. Senate, Murphy is again the youngest of all candidates in the field. But his campaign message could be that of a man decades older.

Now a 39-year-old married father with two children at home, Murphy is emphasizing his years of experience in public office, his demonstrated know-how and relationships in the nation's capital as he faces a challenger in Tuesday's Democratic primary, Susan Bysiewicz, the former secretary of the state, and his likely opponent in November, Republican Linda McMahon.

"Connecticut needs a senator who has a record of standing up for the middle class and winning big legislative fights, and that's been my history," Murphy said in one of several recent interviews. "I think with respect to the other candidates in this race, there's a lot more guesswork. There's not going to be time for learning on the job."

Life has been especially busy for Murphy since his swearing-in in January 2007. He has shuttled by plane nearly every weekend between Washington and his Cheshire residence. Now he's juggling congressional duties with family commitments and his statewide campaign to replace the retiring U.S. Sen. Joe Lieberman.

"It's not easy to run for a statewide office when you're a sitting member of Congress," Murphy said. "But my hope has always been that if I'm doing a good job as a member of Congress for my towns, then that's a pretty good advertisement for my name to be Connecticut's senator."

Murphy is a liberal Democrat endorsed by MoveOn.org who votes with the majority of his party 93 percent of the time, according to an analysis by the Participatory Politics Foundation's website, OpenCongress.org. He is co-chairman of the Center Aisle Caucus, a bipartisan group of lawmakers committed to civility and cooperation. The several dozen members make a point of sitting together during the president's State of the Union address.

Murphy also co-founded the Buy American Caucus and has pushed "Buy American" measures to encourage the Pentagon to use more onshore defense contractors.

One of his earliest efforts as a new congressman was organizing a group of fellow freshmen to request a new independent body that would handle misconduct complaints against members of Congress. "I remember getting the stinkeye from a lot of veteran Democrats and Republicans when I led that effort, but it was the right thing to do," he said.

Although Murphy's bill was unsuccessful, he was a part of the movement that established the Office of Congressional Ethics.

In 2010 Murphy wrote a successful bill that tripled the number of federally financed supportive housing units for people with mental and physical disabilities. "I've always thought that one of the most important jobs of government is to stick up for the most vulnerable among us," he said.

He also had a role in crafting the House version of the Affordable Care Act while a member of the Energy and Commerce Committee. He supports the slightly different version of the health care law as signed by President Barack Obama but wishes that it contained a government-run care plan popularly known as a "public option."

Murphy enjoys frontrunner status in the Senate race. His closest competitor appears to be McMahon, the former WWE executive who narrowed Murphy's lead to 3 percentage points in a June Quinnipiac University poll.

Murphy and Bysiewicz, his opponent in Tuesday's primary, agree on most major issues, including the expiration of Bush-era tax cuts for couples making more than $250,000 and a speedier withdrawal of troops from Afghanistan than that called for in Obama's current plan.

"The biggest difference between Susan and I is you can look at what she'd do in the Senate by reading her website," Murphy said. "You can look at what I'd do in the Senate by watching what I've done in the House of Representatives."

Murphy won the formal endorsement of the state Democratic Party at the spring convention. He is endorsed by the majority of Connecticut's big labor unions and statewide office-holders. His campaign has raised a total $5.5 million, with $2.5 million cash on hand, according to the latest filings.

"I'm supporting Chris Murphy, the candidate who can help me break the gridlock and get results," declared U.S. Sen. Richard Blumenthal, D-Conn., in a Murphy television spot.

A spokeswoman for Lieberman said the departing senator has no plans to endorse a successor.

State Sens. Andrea Stillman, D-Waterford, and Andrew Maynard, D-Stonington, will both be voting for Murphy rather than Bysiewicz next week.

"I had an opportunity to work with him in the legislature, and I know what a good job he did there and what a good grasp of the issues he had," Stillman said. "It's not an easy decision - it's two good people - but I do believe that Chris Murphy is the better candidate."

The eldest of three children, Murphy was born in White Plains, N.Y., to a lawyer father and a mother who was a teacher. His parents - both Republicans - soon moved to Connecticut.

Murphy describes the household as comfortably middle class. However, his mother, Catherine, had grown up poor in the Mount Pleasant housing project of New Britain and told her children how good they had it.

"We didn't think it was automatic that kids had food guaranteed to be on the table and a roof guaranteed to be over your head," he said.

A run for zoning board

Murphy became the first in the family to get actively involved in politics after taking part in a Connecticut River clean-up project. He soon volunteered for the campaigns of Wethersfield Town Council candidates who he thought would be good for the environment. Those candidates all tended to be Democrats, he said.

Graduated from college, Murphy settled in Southington and successfully ran for the local zoning board. He and two childhood friends shared an apartment within a large house that was once a funeral home. The trio didn't learn until after they moved in that the house was said to be haunted and later inspired the 2009 horror film "The Haunting in Connecticut."

"But we were assured that only the first floor was haunted, and we lived on the second floor," Murphy said, smiling.

In 1998, while a University of Connecticut law student, Murphy decided to challenge the longtime Republican incumbent in Southington's 81st House District seat, Angelo Fusco, whose social conservatism Murphy disliked.

"Most people in the Democratic Party in Southington patted me on the head and wished me well in what they thought was a suicide mission," he recalled

But Murphy knocked on 8,000 doors from spring through Election Day. He won the race by 815 votes, a stunning upset.

"The main reason is he worked very hard. I think he wanted it more," explained one Southington town councilman to the local press.

In the General Assembly, Murphy was a co-chairman of the legislature's Public Health Committee and authored legislation that banned smoking in the workplace and increased state investment in stem-cell research.

Murphy later moved to Cheshire to be in the right congressional district to challenge Nancy Johnson in 2006. He won an especially bitter race with tit-for-tat negative campaign ads. He was outspent 2 to 1.

"Most of the political and legislative fights that I've taken in have been ones where the odds didn't look too good at the outset," he said. "But a funny thing happens when you work really hard - you change the odds."

McMahon targets Murphy

Although facing her own primary challenge on Tuesday from Republican Christopher Shays, a former congressman, McMahon is focused on Murphy. In one of her latest TV ads, she touts the superiority of her jobs creation plan to Murphy's.

"It's been pretty clear for quite a while that our real opponent for November is Chris Murphy, and we intend to take every opportunity to draw a contrast between Linda's plan to cut taxes for the middle class and Chris's complete lack of a jobs plan, despite 13 years in office," Tim Murtaugh, McMahon's campaign spokesman, said this week.

Murphy had McMahon on his mind as well during a visit Wednesday to Electric Boat in Groton. With his shirt sleeves rolled up and eyes squinting in the bright sunlight, the congressman stood outside the shipyard gates greeting workers during a shift change. He was accompanied by an entourage of campaign workers and supporters.

"I'm running for U.S. Senate here. I've got Linda McMahon on the other side," he said in one exchange. "These guys are making sure that even though we're going to get outspent, we don't get outmanned."

He took media questions about McMahon's new "jobs plan" ad.

"We knew Linda McMahon's attack machine was coming, and I wear it as a badge of honor that she thinks she has to start it so early," Murphy said, later adding, "My plan is rooted in what's going to help the middle class. Linda McMahon's plan is rooted in what's going to help her."

Also standing nearby was U.S. Rep. Joe Courtney, D-2nd District, the candidate's expert guide to everything submarines.

"Chris and I came in in 2006. We walked through the ring of fire together," said Courtney, a fellow member of that year's freshman House class. "I just think he's a super candidate, a hard-working guy, and he's really well positioned to do good things for the state."

Courtney briefly explored making his own run for the U.S. Senate after Lieberman made clear his retirement plans. But after long conversations with his wife, Audrey, and others, he concluded that his place is the 2nd Congressional District.

"I've enjoyed this district and this seat," Courtney said, "and I'm more of a House of Commons guy than a House of Lords guy."

EB worker Pat Buzzee, 59, of North Stonington, president of the 400-member machinists' union, said Murphy will get his vote this year.

"What can you say bad about a guy who has a 'Buy American' plan?" Buzzee said.

j.reindl@theday.com