The tactic will work only as long as all three commissioners in the Democratic bloc agree not to close an investigation and not to defend the F.E.C. in court on a particular case. Of the three, only Ms. Weintraub would agree to an interview. The other Democratic-aligned commissioners are Shana M. Broussard, who is the current chair and was appointed last year, and Steven T. Walther, who was appointed in 2006 and who F.E.C. insiders say has been largely checked out of the day-to-day functioning of the agency.
Some of the sharpest critics of the F.E.C.’s dysfunction described the Democratic tactic as something akin to a least bad option.
“Campaign finance laws are routinely ignored and corruption is rampant,” said Stuart McPhail, senior litigation counsel at Citizens for Responsibility and Ethics in Washington, which regularly files F.E.C. complaints. “This path is the best in a broken system.”
It is not just a theoretical debate about tactics; some campaign finance cases are already playing out in court. In one current case, lawyers for a nonprofit, Iowa Values, that was accused of failing to register as a political committee are seeking to have the lawsuit against the group dismissed, accusing some F.E.C. commissioners in a memo of “taking their marbles home when they lose” and not closing cases.
There is another important, if obscure, legal factor in play. Currently, the federal courts give almost total deference to the F.E.C. when it decides not to pursue cases — even in the event of a 3-3 split — if commissioners cite “prosecutorial discretion” in their reasoning. Such cases are, more or less, not eligible for legal appeals.
“All the Republican commissioners need to do is include the magic words ‘prosecutorial discretion’ and a court will then decline to review the action,” said Paul S. Ryan, vice president for litigation at Common Cause, who has regularly filed F.E.C. complaints.
Indeed, Republican commissioners recently deployed that exact phrase — twice — in dismissing an investigation into whether Mr. Trump violated election laws with the payment of $130,000 to the pornographic actress Stormy Daniels in 2016 to keep her from publicly discussing her relationship with him.