EVEN IN a season of political chicanery, the campaign of Rep. Donna Edwards, a Democrat running in the primary for U.S. Senate in Maryland, stands out for having twisted the truth so extravagantly that her message provoked the ire of the White House.

The televised ad that elicited the Obama administration’s rebuke this week was the work of a nominally independent pro-Edwards super PAC known as Working for US, but the message dovetails with the candidate’s own. The White House objected because the ad falsely implied that President Obama supports Ms. Edwards. Its underlying message — that Ms. Edwards is an unbending foe of the National Rifle Association, while her opponent, Rep. Chris Van Hollen, is squishy — is equally false.

We have endorsed Mr. Van Hollen in the April 26 primary, and ordinarily we might not write again. But instead of fighting the race on the merits, Ms. Edwards insists on repeating a slander that strikes us as beyond the pale. There is a real contrast between the two candidates, but it’s not their views on gun control. The more accurate distinction is that Ms. Edwards is an ineffective advocate, while Mr. Van Hollen has crafted actual legislation to chip away at the gun lobby’s power.

Ms. Edwards, for all her smarts and political savvy, is like many members of Congress: more about posturing than achievement. Mr. Van Hollen, by contrast, was a key sponsor of a state law requiring trigger locks on handguns when he served as a state legislator, and in Congress he has crafted legislation to encourage states to require handgun permits and background checks. Both Mr. Van Hollen and Ms. Edwards have F ratings from the NRA.

Nonetheless, she has attacked him, and encouraged the Working for US super PAC to attack him, for having cut a deal with the NRA on a bill unrelated to gun safety — a 2010 measure to force more transparency in campaign finance. Democrats, including Mr. Obama and most of the Congressional Black Caucus, backed the bill overwhelmingly.

Ms. Edwards voted against the bill because it exempted the NRA (as well as the Sierra Club) from disclosure requirements aimed at corporations, unions and nonprofits. The NRA carve-out was the price of attracting support from Democrats in conservative districts, whose votes ensured the bill’s passage in the House. (It later failed in the Senate.)

Now Ms. Edwards, with an assist from a shadowy super PAC, says she would never have cut such a deal. Her purity explains her ineffectiveness.

The fact that the Congressional Black Caucus has refused to endorse her, and so many colleagues and local officials are supporting Mr. Van Hollen, is no accident. It’s because Mr. Van Hollen gets things done.