WASHINGTON – With his fight for gun control, defense of the Affordable Care Act and clashes with President Barack Obama on foreign policy, Sen. Chris Murphy broke with a Senate tradition that freshmen should be seen and not heard.

"I don't think there's a waiting period anymore for freshmen," Murphy said. "My constituents did not elect me to be a shrinking violet."

Ron Schurin, political science professor at the University of Connecticut, said Murphy "has had a little bit higher visibility than your average freshman senator.

"And he's not been someone who has stood in the shadows of senior senator" Richard Blumenthal, Schurin said.

Having represented Newtown in the House of Representatives before he was elected to the Senate in 2012, Murphy started the 113th Congress with a path set for him.

He became a forceful critic of colleagues who would not support gun control, saying they were complicit in the slaying of 20 first-graders and six women at Sandy Hook Elementary School. He also became Public Enemy No. 1 for the gun lobby by attacking the National Rifle Association with a series of reports. One showed the organization did not have much impact on the 2012 elections, despite spending millions of dollars. Another showed a disconnect between the opinions of gun owners and the NRA.

Murphy, 41, favored much tougher gun control measures, including a total ban on assault weapons. But he said his biggest disappointment in the 113th Congress — and his political career — was Congress's failure to approve a much more modest bill that would expand FBI background checks of gun owners.

"I've never been as personally and emotionally invested in any issue," he said.

He also brought his hard-charging ways to the bitter congressional debate over the Affordable Care Act. While other Democrats were trying to avoid the political storm that resulted from the botched rollout of the law, Murphy volunteered to be the health care law's chief protector in the Senate.

Although Democrats once hesitated "to defend the law at full volume," Murphy said he's gratified that as more Americans seek health coverage under the law, Democrats no longer balk at embracing it.

According to the Sunlight Foundation, a nonpartisan, nonprofit organization that advocates for open government, Murphy introduced 25 bills in the 113th Congress. Two became law.

One, which Murphy had once sponsored in the House, was introduced in that chamberby Rep. Elizabeth Esty, D-5th District, in this session. It had never passed the Senate until this year. It requires the Federal Energy Regulatory Commission to reinstate expired licenses for hydropower dams at two old mills on the Farmington River so they can once again produce electricity.

The other, called the Honor Flight Act, establishes a process to provide expedited airport screening for veterans traveling to visit war memorials.

Gary Rose, head of the political science department at Sacred Heart University, said Murphy could not point to any huge legislative victories, "but to be fair, that's difficult for a freshman senator." In addition, the 113th Congress was an unproductive one in terms of the amount of legislation passed.

Prospects of getting legislation approved are likely to dim for Murphy – and all other Democratic senators —now that the GOP has taken over the Senate. .

Murphy's reputation in the Senate, however, is not being built on legislation. Besides his high-profile roles on gun control and Obamacare, Murphy came to national attention in September 2013 when he told Obama — who called the senator at home — that he could not back the administration's policy on Syria.

"I can't say that it was a comfortable position to be in, having a public dispute with the president so early in my freshman term," said Murphy, who sits on the Senate Foreign Relations Committee.

He also later clashed with the Obama administration over its plan to arm Syrian rebels to fight Islamic State militants.

Murphy said he became wary of U.S. military involvement because of what he's perceived to be the failures of the wars in Iraq and Afghanistan. The United State should be able to lead without exerting military power, he said. "I'm passionate about American's role in the world."

He said a high point of the past two years was traveling to Kiev, the capital of Ukraine, with Sen. John McCain, R-Ariz., in December 2013 to speak to protesters who were displeased with their government's relationship with Moscow.

Murphy called it "a truly history-making moment."

Schurin said he was impressed when Murphy's staff, shortly after he was elected to the Senate, contacted the University of Connecticut's political science department and asked students to submit questions the senator could bring up at a Foreign Relations Committee hearing.

"It was a nice gesture," Schurin said.

Murphy said his interest in foreign affairs does not interfere with representing Connecticut interests in the Senate. He also said it's a tradition to have Connecticut senators involved in foreign affairs, noting the international interests of former Sens. Joe Lieberman and Chris Dodd.

"I think he's balancing the two," Rose said of Murphy's domestic and foreign agendas.

As a congressman representing the 5th District, Murphy "had pretty high marks" taking care of constituents, Rose said. "So I would think that would translate as good constituent service in the Senate."

Murphy highlights a Connecticut company every week as "Murphy's Monday Manufacturer," has spent a day with a homeless man in New Haven, and hopped on buses in Meriden, Bridgeport, Stamford, Hartford, Torrington, Waterbury and New Haven "to hear what's on people's minds."

Although Murphy said it's easier to work on a bipartisan basis in the Senate than in the House, GovTrack.us shows that of the 144 bills Murphy co-sponsored in 2013, only 16 percent were introduced by a Republican.

GovTrack.us also says Murphy has one of the best voting attendance records in the Senate, having missed only four of the 657 votes cast.

Besides his seat on the foreign affairs panel, Murphy is a member of the Joint Economic Committee and the Health, Education, Labor and Pensions Committee.

Senate leaders have made note of Murphy's vigorous defense of the Affordable Care Act and have also given Murphy a seat on the Senate Appropriations Committee in the new Congress.

"I am not going to be shy about using my seat on appropriations" to steer federal funds to Connecticut, Murphy said.

His willingness to join a political fight also means Murphy is likely to be on the attack in efforts to thwart the GOP's agenda this year.

Murphy said he'll also play defense.

"Republicans are not going to back down from their efforts to gut the ACA," he said.