With the nominations fight between Senate leaders and the White House growing more tense by the day, Sen. John McCain (R-Ariz.) by summer’s end may find an unlikely guard standing between him and the vault holding his presidential campaign money: Majority Leader Harry Reid (D-Nev.).

McCain’s campaign declined to outline his options should the Federal Election Commission’s lights remain off through the summer, preventing the necessary FEC signature on roughly $85 million in public financing that McCain needs to take on his likely opponent, cash-flush Sen. Barack Obama (D-Ill.).

“We’re pleased that the White House has selected the final nominee, someone well known to the Senate, reflecting the priority of getting a full Commission functioning again,” McCain campaign spokesman Jeff Sadosky wrote in an e-mail late last week. “Because the Senate Rules Committee has already reported out favorably the names of the other existing nominees prior to recess [Thursday], we are hopeful that a full slate of FEC nominees can be quickly confirmed by the full Senate when it returns from the Memorial Day recess.”

But the McCain camp’s rosy outlook for reconstituting the agency may be easier said than done. Initially expected to free up the FEC logjam, former Justice Department lawyer Hans von Spakovsky’s decision to withdraw his nomination 10 days ago has only folded the protracted FEC nomination fight into an even larger donnybrook between Senate leaders and the White House.

Talks imploded Thursday night when a deal on Steve Preston, President Bush’ choice to be the next secretary of Housing and Urban Development, fell through.

Afterwards, Reid spokesman Jim Manley told Roll Call that the FEC could be collateral damage to the pre-recess showdown.

“So, in the end, Republicans blocked an attempt to confirm a Housing secretary on a very tight schedule,” Manley said. “They set back efforts to get a fully functioning FEC up and running and left dozens of nominees twisting in the wind.”

The White House claims it is “working hard” to fast-track the FEC nomination of Matthew Petersen, a Senate Rules and Administration Committee GOP staffer who is expected to be nominated for the FEC’s sixth commissioner slot.

Administration spokeswoman Emily Lawrimore declined to speculate on exactly how long Petersen’s background check may take. Rules Chairwoman Dianne Feinstein (D-Calif.), however, said Wednesday that it likely would take a month or more to vet a new nominee, pushing off Petersen’s confirmation vote — and perhaps the fate of the FEC and McCain’s money — indefinitely.

If formally nominated, Petersen would fill out an FEC nomination slate that includes fellow Republicans Don McGahn and Caroline Hunter and Democratic picks Cynthia Bauerly and Steven Walther. The five would join Democrat Ellen Weintraub, currently the agency’s lone commissioner.

Senate Democrats have said they would hold a vote soon on the slate without Petersen, a deal they claim would have the agency back at work dispensing advice, policing campaigns and, come September, signing off on McCain’s money. But with a one-vote disadvantage on the commission until Petersen passes Senate muster, Republicans appear willing to wait out the process until the White House formally ships over his nomination.

Ahead of the Memorial Day recess, White House spokesman Tony Fratto chided Senate leaders — primarily Reid — for playing politics with scores of executive branch appointments, including the five at the FEC and the top HUD job.

“Something we want to mention at the end of this period in Congress … we’ve had an ongoing dispute with the U.S. Senate to try to get our nominees confirmed,” Fratto said. “Today we have over 240 nominations pending on the Hill for important positions.”

And should the nominations fight last through the summer, election law experts argue that McCain would have no choice but to reach for Plan B to release the roughly $85 million in Treasury Department cash that he’s expected to take.

McCain’s primary options: ask a judge to release the money or persuade House and Senate colleagues to change which agency OKs the funds.

Election lawyer Ken Gross of Skadden, Arps, Slate, Meagher & Flom LLP said both of McCain’s potential options are “unwieldy and awkward processes” that are “not contemplated in the law.” But even more, Gross speculated, any McCain plan to tweak the law likely would be fraught with political peril.

“The legislative fix would require a private bill and legislative changes to the Federal Election Campaign Act, which would require a law passed by a Democratic Congress … to fund a presidential campaign of a Republican candidate,” Gross said.

Manley said Reid would block any maneuvering by McCain to tweak federal campaign laws in his favor.

“We would not be willing to entertain special legislation because it would not accomplish the broader goal of having a functioning FEC during the election,” Manley said.

So given the likely political hazards of trying to change the law, Gross said McCain could ask a judge to order the Treasury Department to cut his campaign a check — until now an uncharted prospect for a presidential campaign.

“Under the statute the FEC has to review an application; if it meets all of the requirements, [the FEC] notifies the Treasury Department to release the funds immediately after the nomination,” Gross said. “There is no procedural mechanism within the law for such a lawsuit: sue the Federal Election Commission, sue the Treasury Department?”