Rep. Donna F. Edwards and a co­terie of unhappy Montgomery officials launched a public campaign against a proposed map of Maryland congressional districts Tuesday, aligning themselves against Gov. Martin O’Malley and other fellow Democrats in Annapolis.

The map was unveiled last week by O’Malley’s redistricting advisory committee, and the governor will submit a final version of the new lines for consideration by a special session of the General Assembly that begins Monday.

Under the proposal, Democrats would stand a fighting chance of winning Rep. Roscoe G. Bartlett’s (R) 6th District, which would lose much of Frederick County to Rep. Chris Van Hollen’s (D) 8th District and take on a slice of western Montgomery County in return. That could give Democrats a 7 to 1 edge in the state delegation.

But the plan would also take away the portion of Montgomery that Edwards represents, stretching her 4th District from Prince George’s into Anne Arundel County instead. Rep. John Sarbanes’s (D) 3rd District would also take a portion of Montgomery.

The result, Edwards said Tuesday, would be that Montgomery — a county where minorities make up the majority, according to 2010 Census data — would be splintered into three districts, all likely represented by white men.

“I have been one of the strongest proponents as a Democrat of drawing a seventh district for Democrats,” Edwards said in an interview Tuesday. “But we can accomplish that in a different way. . . . Where I have a real disagreement is in making superior the political interests to the minority voting rights interests.”

The criticism expressed by Edwards and some in Montgomery, however, was not shared by all African Americans, and some with knowledge of the negotiations over the map questioned Edwards’s motives, saying she seemed primarily focused on maintaining a district that would best help her win reelection.

Del. Melony G. Griffith (D), chairwoman of the Prince George’s delegation in the House of Delegates, questioned the logic that Montgomery couldn’t or wouldn’t elect an African American given that it has a black county executive and council chairman.

The new map, Edwards said, would reduce the black voting-age population in her district by nearly 2 percent and would cut the percentage of minorities in Van Hollen’s district by a much larger amount.

“It’s difficult for me to understand how given that growth you’d see a reduction in the percentages in minority populations in each congressional district,” Edwards said.

At a news conference in Rockville on Tuesday, a score of state and Montgomery officials said they would urge O’Malley to scrap the proposed map. If he doesn’t, the state NAACP will probably sue the state, said Elbridge James, a state NAACP official.

“The NAACP is hoping — and that is a very loose word, hoping — that the governor . . . [will] move off of this map to something that . . . won’t be open to court challenge before Monday’s session,” he said.

The officials, who were mostly minority, said the map would dilute minority voting power and violate the federal Voting Rights Act. “This really does disembowel Montgomery County in terms of communities of interest,” said County Council member Nancy Floreen (D-At Large).

Two sources close to the negotiations said Edwards’s stance was not unexpected and appeared to be the culmination of months of uneasy negotiations between her and other Democratic members of Congress and O’Malley’s office. The sources said that in closed-door meetings, Edwards at one point had agreed to give up part of her district to help the party become more competitive in the 6th District. But they said she would never agree to a particular plan.

“From the beginning, she has been all over the place on what she would support and what she wouldn’t support,” said one of the two officials, who both spoke on the condition of anonymity to freely describe private negotiations. “Ultimately, I think she doesn’t want a primary election in Prince George’s, and that’s what this is all about.

By the numbers, Edwards’s district will remain one of the most solidly African American in the country, and arguably the most reliably Democratic in Maryland.

But Edwards’s strength has come, in part, from her ability to appeal to multiple types of Democratic voters, those in Prince George’s, Montgomery and beyond. She has raised roughly twice as much money from voters in Montgomery as in Prince George’s, and even more money from the District, New York and California.

In her new district, voters in Prince George’s alone could decide the Democratic primary, meaning that in the county’s often capricious political culture, another person with countywide name recognition and grass-roots support could potentially mount a competitive primary challenge.

Edwards, who won her seat in 2008 by ousting Albert R. Wynn in the Democratic primary, said fear of a similar challenge played no role in her opposition to the redistricting map. “I challenged in a primary, so far be it for me to say there should be no primary challenges,” she said.

Edwards raised eyebrows among some colleagues on Capitol Hill last week when she was seen on the House floor reviewing redistricting maps with Bartlett. Asked whether she was working with Bartlett against the new map, Edwards said: “Absolutely not. I’m a Democrat.”

Edwards’s opposition has already drawn the ire of some of her colleagues in the national Democratic establishment and in Maryland. In attacking the map, she is going after a plan backed by O’Malley and co-authored by state Senate President Thomas V. Mike Miller Jr. (D-Calvert) and House Speaker Michael E. Busch (D-Anne Arundel).

Some Montgomery officials defended the map Tuesday.

Council member Roger Berliner (D-Bethesda-Potomac), a self-described “old-fashioned Democrat,” said he is fine with O’Malley’s proposal because he wants an extra seat for his party in Congress.

“I see no over-arching issues that make [the map] inappropriate,” Berliner said.

Staff writers Victor Zapana and Robert McCartney contributed to this report.