A couple of liberal black female politicians from Prince George’s and Montgomery counties are challenging the Maryland Democratic establishment on behalf of minorities and the D.C. suburbs. And I say it’s about time.

One is Rep. Donna F. Edwards (D), the Prince George’s-based congresswoman who, in her second term, is a vice chair of both the liberal and progressive caucuses in the House. The other is Montgomery County Council President Valerie Ervin (D-Silver Spring), who is also emerging as a potent local political figure.

The two have rattled the power structure this week by publicly criticizing the plan put forth by Gov. Martin O’Malley’s handpicked committee to redraw the map of the state’s eight congressional districts following the 2010 Census.

Edwards and Ervin, who are allies and speak regularly, complained that the proposed districts dilute minorities’ representation so much that they might violate the 1965 Voting Rights Act.

Ervin also organized and led a remarkable news conference in Rockville on Tuesday in which a “rainbow coalition” of white, black, Latino and Asian elected officials from Montgomery assailed the redistricting plan.

In Democratic politics, this is the equivalent of bringing up the large-bore howitzers. Imagine how it’s going to look for O’Malley, chair of the Democratic Governors Association, if the NAACP follows through on warnings it might sue the state.

Edwards, Ervin and their supporters face an uphill battle when the state legislature takes up the redistricting plan starting Monday. The establishment probably has enough muscle to push the plan through.

Still, it’s good to see somebody stand up to the party leaders and object to their taking Democratic voters in the D.C. suburbs — especially minority ones — for granted.

There’s little question the proposed voting map makes it harder for minorities in Montgomery to exert influence as individual groups or collectively. That’s because it divides the black, Latino and Asian communities among three congressional districts.

As a result, although the minority population in Montgomery has surged since the last census, minorities are likely to have less clout than before in Congress.

“I think what the governor missed was it’s a community that’s no longer going to sit silent. For a long time, we’ve been taken advantage of,” Ervin said.

The plan’s defenders say the gerrymandering was necessary to accomplish its primary goal: ousting Rep. Roscoe G. Bartlett (R) in Western Maryland. But critics say it went beyond that, and busted up Montgomery’s minority neighborhoods in the process, in order to help some well-connected Democratic politicians.

“I cannot support this plan in its current form, given that minority representation interests appear to have been sacrificed for . . . political interests,” Edwards said.

Moreover, the plan was clearly designed in part to punish Edwards and clip her wings. Her redrawn district no longer stretches into Montgomery, a reliable source of campaign funds and liberal supporters. Instead, along with her base in Prince George’s, she’d now be representing a more conservative swath of Anne Arundel County.

The payback isn’t surprising, given that Edwards has always been a bit of a maverick. Her win in 2008 came out of a grass-roots campaign that unseated the establishment’s favored incumbent Albert R. Wynn.

Moreover, Edwards has recently tangled with one of Maryland most powerful politicians, House Democratic Whip Steny H. Hoyer.

Edwards’s relationship with Hoyer cooled in last summer’s debt negotiations, when she took a more liberal position than his on Medicare and Social Security. Hoyer also was unhappy that Edwards opposed his original redistricting plan, focused on picking up a Democratic seat on the Eastern Shore.

Although few will say so openly, the redistricting plan is also annoying for D.C. area voters, because it’s drawn partly to help a Baltimore-based Democrat, Rep. John Sarbanes, at the expense of those from our area. The state party establishment is grooming Sarbanes to eventually run for the U.S. Senate, where his father, Paul S. Sarbanes, served.

Sarbanes’s district is mostly limited to the Baltimore area. Now it’s being extended into Montgomery — at Edwards’s expense — giving him more access to campaign contributions and media exposure.

The change is also unhappy news for Rep. Chris Van Hollen (D), who is thinking of a U.S. Senate run himself and whose Montgomery-based district is becoming less attractive.

Van Hollen is too good a team player to complain publicly, but I’m glad Edwards and Ervin think differently. Even if they lose, the insurgents have flexed their muscles in a way that will hopefully prompt party leaders to treat Montgomery and Prince George’s Democrats with more respect.

I discuss local issues at 8:51 a.m. Friday on WAMU (88.5 FM).