IN A SMALL STATE such as Maryland, it might seem like a stretch to collect more than 56,000 signatures on a petition to repeal a political map because the boundaries have been excessively gerrymandered. But it turned out to be eminently doable once Marylanders got a look at the congressional district map rammed through the legislature last year by Democrats — a map with lines so tortuous that a federal judge likened the shape of one congressman’s district to “a broken-winged pterodactyl, lying prostrate across the center of the state.”

The success of the petition drive, which attracted at least 3,000 more signatures than needed, triggered a referendum that will be on the ballot in November. If the redistricting is rejected, Democrats will have to return to the drawing board.

That would be a salutary outcome, both for Maryland and for the two-party system — or what’s left of it in the Democratic-dominated Free State. If voters reject the map, whose sole purpose is to add a seventh safe Democratic seat to the existing six in the state’s eight-member congressional delegation, it would send a clear message to the leadership in Annapolis that partisanship without limits is an affront to democracy.

The gerrymandering of Maryland’s congressional district map is not unique; in other states Republicans have taken similar liberties. And while a federal court ruled that the Maryland map does not discriminate against African American voters, as some groups charged, that doesn’t make it a fair blueprint.

The latest redistricting in Maryland, following the 2010 Census, is such a barefaced manipulation that it stands as an embarrassment to the state, lampooning the idea that electoral districts should respect jurisdictional boundaries and communities of interest. Instead, heavily Democratic counties were sliced up into slivers, shards and oddly shaped scraps that were used to offset and outweigh Republican strongholds elsewhere. All of it was meant to protect entrenched incumbents — and to target the state’s senior Republican House member, Roscoe G. Bartlett, one of just two GOP congressmen from the state.

Gov. Martin O’Malley (D) has sneered at the petition drive and suggested that he won’t push for a major overhaul even if voters throw out Maryland’s crazy-quilt map at referendum. That’s the sort of arrogance that could prompt voters to reassess Maryland’s de facto status as a one-party state. It’s one thing when politicians flip democracy on its head by choosing their voters; it’s another when they scoff at voters who notice, and object, to being treated as pawns in an insiders game.

Brazenly partisan redistricting leads to non-competitive elections whose winners need never fear a plausible challenge from the opposing party. The result is a Congress stuffed with incumbents who, lacking any incentive to compromise, provide the building blocks for political paralysis. It’s a pity that Mr. O’Malley has not pushed for a bipartisan or nonpartisan redistricting system of the sort that has been adopted in about a dozen states and could help produce more competitive districts, more moderate candidates and a political system that actually functions.