Rep. Donna Edwards’ backing of a surging candidate over the establishment pick in a contentious Congressional primary earlier this month shocked Maryland insiders, but it was only the latest show of her increasingly independent streak in the close-knit Congressional delegation.

The Democrat said her colleagues should not have been surprised.

“When my colleagues went to endorse Rob Garagiola, nobody asked me for my opinion about that,” Edwards said in an interview last week. “And I didn’t ask anybody else. I did what I thought was the right thing to do, and I made a decision, just like they did.”

Edwards supported businessman John Delaney, who ousted Garagiola, the state Senate Majority Leader and a close ally of House Minority Whip Steny Hoyer, in the contentious April 3 primary to run against vulnerable GOP incumbent Rep. Roscoe Bartlett.

During redistricting, the seat in question was drawn with Garagiola in mind and with Hoyer’s blessing.

Critics of Edwards said her late endorsement of Delaney paints her as opportunistic and an outsider to the delegation. She endorsed after President Bill Clinton weighed in for Delaney and after the race turned in his favor.

But others note that Edwards scored a major win that could help her down the line as she considers a leadership post under the Dome or even a statewide race.

Either way, the move underscored maverick tendencies that are viewed by some as unhelpful to her future in the House.

“I think Donna has exhibited an edginess that is not helpful to her long-term effectiveness,” said a source with close ties to the delegation. “She’s taken on the whip publicly and criticized him in front of the Caucus. She backed down and apologized, but subsequent behavior would suggest those are her real sentiments. I think she’s created a sense of alienation in the Maryland delegation, top to bottom.”

Indeed, Edwards dressed down Hoyer last summer during the debt ceiling debate over her concerns about Medicare and Social Security.

While other Democratic colleagues shared her goal of protecting those entitlement programs, witnesses to the exchange said none espoused such heated rhetoric in delivering their message as Edwards.

Multiple sources would not go on the record to discuss Edwards, but several cited her approach as overly aggressive. One said the Maryland delegation’s decision not to consult her on the Garagiola endorsement illustrates its level of frustration with her.

It was not the only issue with Edwards this cycle; she fought ferociously against the new Congressional map released in October. At the time, Edwards made no secret of her disgust with the lines. In an interview in October, she called the map “deeply flawed.”

Edwards said there is little residual ill will from the debate over the map or the primary in western Maryland, saying, “I think it’s water under the bridge.”

Rep. Elijah Cummings backed that up. “I don’t think there were fences that needed to be mended,” the Maryland Democrat said.

Even Edwards’ critics say her compelling background and media savvy make her a rising star. She is a regular on cable news shows and a frequent messenger in partisan policy debates, most recently during the Supreme Court hearings on the health care law, the budget and women’s issues. She co-chairs the Democratic Congressional Campaign Committee’s Red to Blue program.

Edwards is on the Ethics Committee, an unappealing assignment ambitious lawmakers frequently take to curry favor with leadership, and is an active member of the Congressional Progressive Caucus and the Congressional Black Caucus.

Still, one senior staffer to a CBC member said Edwards “is extraordinarily ambitious and super smart, but a little bit … what’s the best word to put it? I guess the way to put it is that she kind of plays by her own rules and there’s not necessarily playing to the graces of the overall structure.

“When you’re winning, that ego isn’t as damaging. But when you’re not, it becomes a challenge,” the staffer cautioned.

In the Delaney fight, Edwards’ candidate won, but she did not walk away unscathed. The typically liberal lawmaker managed to rattle the AFL-CIO, which had backed Garagiola. The group’s Maryland president, Fred D. Mason Jr., wrote a highly critical memo of her decision.

“She had been asked to endorse Rob Garagiola, and barring that to endorse no one,” Mason wrote, according to the Baltimore Sun. He added that her endorsement of Delaney would “certainly be considered in our future relationships.”

Rep. Emanuel Cleaver, chairman of the CBC, acknowledged Edwards is “not a shrinking violet” and pointed out that others “sometimes have difficulty with assertive women.” But the Missouri Democrat nevertheless had high praise for his “extremely bright” colleague.

“I think she is probably someone who in time is going to be a candidate for some leadership position,” he said. “She’s not saying that, I’m saying that.”

Edwards certainly knows how to win uphill campaigns. She endured her own contentious primary battle in 2008, when she challenged Rep. Albert Wynn. While most CBC members and the Maryland establishment backed Wynn, they quickly came to support Edwards after she cleared the primary and when she joined Congress. She predicted the same would be true if Delaney wins in November.

“I won in a primary, so I understand primary fights,” Edwards said. “You do what you do and you move on, and I expect the same is going to be true for John as he wins and makes his way into the House.”

On that point, Cummings agreed.

“We’re a small delegation, and we realize we’ve got to stick together. Big time. No matter what,” he said. “And part of our success has been that. And I think all of us are big-picture people, including Donna.”