Passing the GOP health care bill through a fast-track process called "reconciliation" might not be as simple as Senate Republicans had anticipated.

AP/J. Scott Applewhite - apimages.com

In fact, Democratic lawmakers could use the same process to delay a vote indefinitely, Ezra Levin, co-executive director of the progressive group Indivisible Guide, claimed in a tweet thread on Thursday.

What is reconciliation?

Reconciliation a special rule in Congress that allows lawmakers to attach certain bills to the budget. Unlike bills that go through the traditional legislative route, these bills aren't subject to filibuster and require only 51 votes to pass. You need 60 votes to break a filibuster, so without that option, it can be easier to pass a bill through the reconciliation process.

Republican leaders in the Senate are expected to use the reconciliation process to quickly pass their version of the GOP health care bill—and bypass a filibuster attempt from Senate Democrats.

But there's a catch, as Levin pointed out.

"Vote-a-rama."

When the Senate considers reconciliation bills, debates are limited to 20 hours. However, the special procedures "do not limit the number of amendments that can be offered during the Senate’s initial consideration of the bill," according to the Center on Budget and Policy Priorities (CBPP). "As a result, once the 20-hour limit has expired, remaining amendments are considered with little or no debate—a process known as a 'vote-a-rama.'"

The "amendments offered to a reconciliation bill must be germane to the bill," which "prevents the process from getting bogged down by disputes over tangentially related or unrelated amendments, as often happens to other legislation under regular Senate procedures," the CBPP explains.

Levin said Senate Democrats could exploit this loophole by introducing "dozens, hundreds, THOUSANDS" of amendments, which would have to be voted on individually.

"Let’s say it takes about 10 minutes to introduce and then vote on an amendment, a conservative estimate," Levin wrote. If Senate Democrats introduced 40,000 amendments, it'd hold up the vote for 40 weeks and "take us through the 2018 midterms."

His proposal is to use the threat of a prolonged "filibuster-by-amendment" to demand that Senate Republicans allow public hearings on the health care bill.

The "filibuster-by-amendment" tactic was invented, and first successfully implemented, by Sens. James Allen (D-Ala.) and Roman Hruska (R-Neb.) in 1976.

The two senators "ensured that numerous amendments were offered" to an antitrust bill and were "able to tie the Senate up," Shad Satterthwaite, a professor of American history, wrote in a post for ThisNation.com, a site run by educators at the University of Oklahoma's political science department. It took "70 separate roll-call votes" before the senators who sponsored the bill "finally agreed to support an amendment proposed by Allen and Hruska," ending the filibuster.

That said, it's uncertain if Senate Democrats in this session would be willing to use the same tactic to block a vote on the Senate's (as of yet, secret) version of the American Health Care Act (AHCA).