Sen. Bob Menendez is a team player and loyal Democrat, except when he’s not.

No one questions the New Jersey Democrat’s fidelity to the party and progressive causes, but Menendez has a knack for picking high-profile fights with fellow Democrats, including opposing a recent White House judicial nominee, voting against the deal to raise the debt ceiling last summer and trying to block the administration’s evolving policy toward Cuba.

“He is certainly someone who stands up for what he believes in, and sometimes that means standing up against: (A) your own party and (B) what might be popular or convenient,” Menendez spokeswoman Tricia Enright said.

She characterized the relationship as a “push and pull” and noted that he served in leadership during the 2010 election cycle as Democratic Senatorial Campaign Committee chairman and that the party continues to use the fluent Spanish speaker as a bridge to the Hispanic community.

But Menendez has endured a fair amount of flak from his own party and from the media for his positions.

The latest confrontation was over Patty Shwartz, who was nominated by President Barack Obama in October to join the U.S. Court of Appeals for the Third Circuit.

Menendez objected to her appointment — the first time a Democrat has blocked one of Obama’s judicial nominees. Under Senate Judiciary Committee procedures, the process does not move forward until the nominee gets sign-off from both home-state Senators. Sen. Frank Lautenberg (D-N.J.) approved Shwartz’s appointment.

Menendez had claimed Shwartz was not qualified to get bumped up. She currently serves as a magistrate judge for the U.S. District Court for the District of New Jersey. He had in particular raised concerns about her knowledge of campaign finance law.

But after the New York Times and other media outlets drew attention to his hold, Menendez met with Shwartz on Friday and announced that he had changed his mind and would no longer block the appointment.

“After an in-depth discussion today with Judge Patty Shwartz, I am pleased to announce that I am supporting her nomination to serve on the Third Circuit Court of Appeals,” Menendez said in a statement. Shwartz “satisfactorily answered questions covering important legal topics” and “adequately allayed my earlier concerns,” he said.

Menendez had been a lone voice against her. The American Bar Association has given her a “unanimously well qualified” rating, and the White House stuck by her.

Critics said Menendez’s opposition was payback for the federal probe against him during his last bid for office. Shwartz is romantically linked to Jim Nobile, who led a federal corruption investigation against Menendez.

The probe concerned Menendez’s pursuit of federal funding for a New Jersey nonprofit that rented space in a building he owned. No charges were ever brought, and the five-year probe was ended in October.

Menendez’s office dismissed the idea that his opposition to Shwartz was motivated by revenge, and aides said his concern about the nomination stemmed from Shwartz’s qualifications on issues such as the Citizens United U.S. Supreme Court ruling. Democrats and Menendez oppose the ruling in which the high court declared corporations have the right to spend unlimited funds on elections as an expression of their free-speech rights.

Before Friday’s announcement, White House spokesman Eric Schultz had said the White House hoped Menendez would reconsider his opposition to Shwartz’s nomination but added, “We are regretful that the Senator’s motives were questioned.”

Menendez’s aide said that despite the dustups over Shwartz and Cuba, he is still working with the Obama administration on key issues. For example, he was on the Spanish language television station Univision Jan. 8, spreading the word about a new rule proposed by the White House to allow certain undocumented immigrants to remain in America while applying for legal status. The rule is likely to be well-received by members of the Hispanic community, who may face years of separation from family while they apply for a green card.

Still, his opposition to Shwartz put him in a very public dispute with the White House.

“People are questioning whether he really did the right thing by putting this on people’s radar,” said Peter Woolley, director of Fairleigh Dickinson University’s PublicMind Polling Institute.

“I think its hard not to make the connection between her and her boyfriend,” Woolley said.

Menendez also bucked the White House on the deal reached in August to raise the debt ceiling by $2.1 trillion in two separate increases. Under the deal, the increase would be offset by an initial $917 billion in cuts over 10 years and another $1.2 trillion in automatic cuts over 10 years beginning in 2013 divided evenly between defense and nondefense spending. Those cuts were triggered when the super committee failed to hammer out a different deficit reduction package.

Menendez opposed the pact because it was offset with spending cuts that he argued would hurt the middle class.

“I cannot in good conscience support a plan where soldiers, seniors, students, and working families must endure trillions in cuts, while oil companies, billionaires, and corporate jet owners are not asked to pay their fair share,” Menendez said in a statement at the time.

Another point of contention has been Cuba policy. In 2009, Menendez, who is of Cuban descent and passionate about the issue, blocked a $410 billion omnibus spending package because he disagreed with a provision to relax travel restrictions to the island. The New Jersey Senator also held up two other Obama administration nominees in order to win concessions from the White House on Cuba policy.

Eventually Menendez backed off after getting assurance from the Treasury Department that it would narrowly interpret the provision.

But Menendez was criticized for his opposition by senior White House officials, including then-Chief of Staff Rahm Emanuel, and rank-and-file Senators who raised the issue of whether Menendez should get to remain in the Democratic leadership.

His aides stressed that despite the tumult, the Cuba issue was worked out.

Sen. Charles Schumer (N.Y.), head of the Democrats’ policy and communications shop, said in a statement from his office that “on fundamental Democratic issues, Bob Menendez is one of the stalwarts in the Senate and is regarded as a invaluable leader in our party that helps keep us unified.”

Ben Dworkin, director of the Rebovich Institute for New Jersey Politics at Rider University, said Menendez remains a solid progressive vote in the Senate despite a few disagreements with Democratic leadership and the White House.

“Most legislators, Senators certainly, would want to be able to say, ‘I haven’t been in lock step every time, and here is when I haven’t been because I believe in the issue,'” Dworkin said.