A widely popular bill that’s become embraced by the Republican mainstream while losing some key Democratic backers is on the move again, but its chances appear tied to whether members of the Senate reclaim their historical support.

There’s no indication that will happen as Rep. Thomas Massie prepares his bill for markup Tuesday by the House Oversight and Government Reform Committee. But the Kentucky Republican says he hopes the senators will again get behind the Federal Reserve Transparency Act.

“As I collect co-sponsors, it’s literally the easiest bill I’ve ever whipped,” he says. “People are fed up with Washington, they want more transparency. ... In the House it’s not a partisan issue. Somehow it became that in the Senate."

As lead House sponsor, Massie is carrying on an effort launched by libertarian Rep. Ron Paul, R-Texas, and self-proclaimed democratic socialist Sen. Bernie Sanders, I-Vt., in 2009 in response to the Great Recession.

As President Barack Obama settled into office, the audit-mandating measure became embraced by an overwhelming majority of Republicans, along with many progressive Democrats. In 2012, it won 327-98 passage in the House.

At the time, then Democratic Reps. Joe Donnelly of Indiana, Chris Murphy of Connecticut and Martin Heinrich of New Mexico voted in favor. Murphy and Heinrich also co-sponsored the original version.

The bill repassed the House in a 333-92 vote in 2014, and in January the Senate considered a companion bill from Sen. Rand Paul, a Kentucky Republican and then a presidential candidate. Although it had majority support, the bill failed to reach the 60 votes needed to move forward.

Donnelly, Murphy and Heinrich – after elevations to the Senate – voted against cloture for the bill, contributing to its 53-44 failure. Sen. Mazie Hirono – a Hawaii Democrat and another co-sponsor of the original House version – voted against cloture as well, despite also co-sponsoring a near-identical Senate bill the year before.

Sens. Mazie Hirono, Martin Heinrich, Joe Donnelly and Chris Murphy supported Federal Reserve audit legislation before voting against it in January. Getty Images

The four senators aren’t alone in abruptly changing their positions without explanation. In 2012, eight House Democrats who co-sponsored the bill voted against it for reasons their spokespeople would not supply.

The reason for the Senate Democratic caucus’ almost lockstep unity earlier this year is unclear; only Sen. Tammy Baldwin of Wisconsin and Sanders, an independent seeking the Democratic presidential nomination, voted in favor, with one Republican voting against. Publicly offered statements against the bill stressed concern that one clause would open monetary policymaking to excessive congressional oversight.

That clause, however, was included in the 2012 bill supported by Donnelly, Heinrich and Murphy, as well as the Senate bill introduced last year with Hirono as a co-sponsor. It would allow the Government Accountability Office to complete a full audit of the Federal Reserve by striking a 1978 prohibition on review of records in the following four categories:

1. transactions for or with a foreign central bank, government of a foreign country, or nonprivate international financing organization;

2. deliberations, decisions, or actions on monetary policy matters, including discount window operations, reserves of member banks, securities credit, interest on deposits, and open market operations;

3. transactions made under the direction of the Federal Open Market Committee; or

4. a part of a discussion or communication among or between members of the Board and officers and employees of the Federal Reserve System related to clauses (1)–(3) of this subsection.

Ahead of the Senate vote earlier this year, former Federal Reserve Chairman Ben Bernanke said the effort to enhance transparency could have negative consequences by constraining the candor of FOMC discussions and providing a vehicle for intrusions.

“The principal effect of the bill would be to make meeting-by-meeting monetary policy decisions subject to congressional review and, potentially, congressional pressure,” Bernanke wrote.

“The bill would do this by repealing existing restrictions, imposed by Congress nearly 40 years ago, on what the GAO can examine when reviewing the Fed. The most important such restriction blocks the GAO from reviewing 'deliberations, decisions, or actions on monetary policy matters,' as well as 'discussion or communication among or between members of the Board and officers and employees' related to such deliberations. The repeal of the existing restrictions would accordingly allow the GAO to view all materials and transcripts related to a meeting of the Fed’s Federal Open Market Committee (FOMC) at essentially any time and require the GAO, at congressional request, to provide recommendations on monetary policy, including potentially on individual FOMC interest-rate decisions.”

Rephrasing that argument, Sen. Sherrod Brown, D-Ohio, said in January if there's too much oversight “we’ll see many members of Congress pushing the Fed to side with the bondholders and Wall Street on combating inflation rather than siding with Main Street and small businesses and workers in dealing with unemployment.”

Massie jokes that Democrats probably would be more interested in an audit if the Federal Reserve was led by a Republican appointee, and scoffs at arguments a hands-off approach is best for maintaining the Fed's independence to craft policies.

“Maybe an audit would disclose the Federal Reserve isn’t as independent as we think from the executive branch,” he says. “There’s a bit of irony for you: The argument that the Federal Reserve should stay independent could be an argument for an audit!”

A scaled-back audit amendment from Sanders in 2010 – accepted without objection in the Senate – allowed a one-time review of the Fed’s emergency loan practices and revealed $16 trillion in assistance to banks. It followed controversy over about $553 billion in loans given to foreign banks through 2008 with approval from the Fed’s FOMC, using what Bernanke said was not emergency authority.

"This is a clear case of socialism for the rich and rugged, you're-on-your-own individualism for everyone else,” Sanders sniped when the review was complete.

Spokespeople for Donnelly, Heinrich, Hirono and Murphy did not respond to requests for clarification on their current positions or offer an explanation on the apparent evolution of their stances, nor did a spokeswoman for Senate Democratic Minority Leader Harry Reid, who in 2010 professed support for auditing the Federal Reserve.

Their collective votes could put the long-debated bill over 60, if the January vote’s two Republican no-shows – Sens. Ted Cruz of Texas and Dan Coats of Indiana – were also to vote in favor. A third no-show, Sen. Al Franken, D-Minn., opposes the bill, a spokesman says.

Massie says the Democratic senators "have an obligation to explain why they changed in the Senate." He says he's not sure why that would be, but speculates that “maybe they have less pressure from constituents with a six-year term.”

Earlier this year Ron Paul, now retired from Congress, told U.S. News he found criticism of the bill difficult to understand.