Yet as the Senate prepares to begin work on a sweeping voting rights and elections overhaul bill, the two parties are bitterly divided over a proposal to restructure the enforcer of campaign finance rules, a central plank of the legislation. It is a significant reason Republicans oppose the measure so strongly.
The bill would reconfigure the panel from being evenly divided to having a 3-to-2 split, making stalemates far less likely, giving more power to its presidentially appointed chairman and building in stronger enforcement mechanisms.
Senator Mitch McConnell, Republican of Kentucky and the minority leader who has long fought against campaign finance restrictions — including by steering like-minded allies onto the commission — placed revamping the panel at the top of his list of examples of Democratic overreach in a measure he said was stuffed with outlandish ideas.
“First, I would list turning the F.E.C. from the judge into a prosecutor and giving the party of the president the opportunity to harass opponents,” said Mr. McConnell when asked to itemize his objections to the bill. “Completely outrageous.”
He and fellow Republicans argue that the commission’s overhaul would set off a series of back-and-forth partisan campaign investigations each time power shifted in Washington and the makeup of the panel changed.
“I think that is a mistake,” said Senator Richard C. Shelby, Republican of Alabama and a senior member of the Rules Committee that is scheduled to take up the elections and campaign bill in May. “One group will go after the other. With Republicans in control, they will go after the Democrats, and vice versa.”
He also questioned whether it was necessarily bad that the commission often could not agree on enforcement measures.
“Maybe they don’t need to,” he said. “Most things are disclosed, and you all are sure watching,” he said of the news media.
Democrats suspect that Mr. Shelby nailed the true reason that Republicans oppose the overhaul — that they prefer the tightly leashed watchdog that exists now over an empowered election commission that would rigorously carry out the law.
“Republicans want to keep it broken because they want people to be able to skirt the law with impunity,” said Senator Chris Van Hollen, Democrat of Maryland and a proponent of the changes. “The problem is that it is so broken, people have accepted it as the status quo. But campaign finance laws are meaningless if they are not enforceable.”