Senate Majority Leader Mitch McConnell (R-Ky.). (J. Scott Applewhite/AP)

Senate Republicans could vote as soon as next week on legislation that drastically changes the nation's health-care system, and yet nobody but a small group of Republican senators knows what's in it.

That's not normal, say nonpartisan health-care analysts and historians. “I've never seen anything like it, as far as the secrecy,” said Paul Ginsburg, a health policy expert at the University of Southern California.

And it raises this dual question: Are Republicans shielding their work because they don't yet have legislation? Or because they do, and it's unpopular?

And if the secrecy helps them pass a health-care bill, are we witnessing a potential historic shift in the way Washington debates — or doesn't debate — big legislation?

Why this isn't normal

Except for the early years of the 20th century, the Senate has generally voted on legislation that was crafted by members of both parties, said Donald Ritchie, the former official Senate historian.

Senate Republicans aren't doing that. They have been trying to write a bill since May, when House Republicans barely passed a controversial — and largely unpopular — piece of legislation. Senate leadership promptly threw in the trash.

Instead, Republicans set up a group of about a dozen lawmakers — originally, none of them were women —  to come up with something more moderate. Senate Republicans, who have 52 members, can only lose two votes and have something pass. The group is now open to any GOP senator who wants to participate, and they've held three-times-a-week lunch meetings.

But several months later, key lawmakers outside that group still don't know what's in the bill, assuming there even is one.

There are always some kinds of closed-door negotiations on big pieces of legislation.

But at this point in the 2009-2010 debate for the Affordable Care Act, there had been months of public committee hearings that you and I could attend or watch online or read about in the news. Senators had been briefed on what was happening and could answer reporters' questions instead of saying they have no idea what's in the bill. Amendments were offered by both sides.

Ultimately, the final version of Obamacare passed without any Republican support. But, said Jim Manley, an aide to Senate Democratic leadership at the time: “We spent months — at the detriment of the process — trying to get Republicans on board, only to give up. We tried very, very, very hard.”

So why are Republicans keeping a major health-care bill so secret? A few theories.

The secrecy isn't ideal, but it outweighs the blowback

Arguably, Republicans don't want to be doing it this way. The Washington Post's fact checker gave Senate Majority Leader Mitch McConnell (R-Ky.) the equivalent of a flip-flop for accusing Democrats during the Obamacare debate of making secret deals to pass the legislation.

Fact checker Glenn Kessler: "[McConnell] was against secrecy and closed-door dealmaking before; he now oversees the most secretive health-care bill process ever.”

While Obamacare was under consideration, McConnell had strong words for the Democratic majority's tactics, criticizing them for going 'the partisan route.' Now, he seems to be using them. (Meg Kelly/The Washington Post)

But sometimes, a negotiation is so delicate that doing it in public is counterproductive, said Alice Rivlin, a senior fellow of economics and health policy at the Brookings Institution.

Let's say there's a committee hearing for a piece of legislation, and a lawmaker proposes an intriguing compromise. The media starts reporting it, the opposition latches onto it, and then that person who floated the idea is faced with protests in their district and now the idea is so toxic it has to be dropped.

“I am not one who thinks that all negotiations need to be out in the sunshine,” she said.

The more an unpopular bill marinates, the more time you have for opposition to stew

We know House Republicans' health-care bill was a total political dud. But it didn't always start out that way. Repealing Obamacare is a popular idea among Republican voters, but as the House tried to find a way to do that, Obamacare started to get more popular, even among some Republicans.

At one point House Republicans had to pull the bill from the floor because lawmakers in the center and the right of their party were dropping from it.

The same thing happened when Democrats were debating their version of health care — they were close to a deal, then lawmakers went home for a month-long break, were confronted by angry opposition in angry town halls, and it took almost another year for the legislation to pass.

It's very likely that whatever more moderate version Senate Republicans are crafting is unpopular as well, because it's really hard to find a way to sell legislation that could take away health insurance and/or benefits from millions of people.

“When the public sees it, they're not going to like it,” Ginsburg said.

So why share it with the public before you absolutely have to?

If this works, it could change how Washington works

Let's say Republicans introduce their secret legislation sometime this week. The nonpartisan Congressional Budget Office manages to quickly estimate its cost on the federal budget and effect on people's health-care coverage. The Senate votes before going home around July 4, and it passes with all but two Republicans supporting it. (This would all be done under a budget rule called reconciliation, meaning Democrats can't filibuster it).

That would be a remarkable change in the way legislation is debated and passed. And it would be a very tantalizing path for both sides to take in the future. Sure, Republicans are getting blowback now because of the secrecy. But the next time they debate something behind closed doors, the process could normalize a bit more.

Put another way: Both sides would agree that crafting bills in secret isn't the way our nation's founders intended major legislation to pass. But there's a real chance that, if Republicans pull this off, it could be the way Congress passes controversial bills in the future.