A bill set before the United States Senate that would help to restore the net neutrality rules recently repealed by the Federal Communications Commission is just one vote shy of having the support it needs to pass.

The bill, which requires 51 votes in order to pass, currently has backing from the 49 members of the Senate Democratic caucus, including independents Bernie Sanders of Vermont and Angus King of Maine. Susan Collins, R-Maine, is thus far the lone Republican to lend support to the bill.

If the group can successfully convince one more Republican to join its cause, it can enact a Congressional Review Act (CRA) resolution put forward by Senator Ed Markey, D-Mass., that would effectively start the process of halting the FCC’s plan to repeal net neutrality protections put in place by the previous administration.

The CRA would block the Restoring Internet Freedom Order, proposed by Donald Trump appointed FCC Chairman Ajit Pai and passed on party lines in December , which intended to reverse the decision to classify internet service providers as common carriers under Title II of the Communications Act.

The classification was first enacted in 2015 by the FCC under President Barack Obama and provided the agency with the ability to ensure internet service providers did not violate net neutrality—a concept that insists that all data must be treated as equal and prevents ISPs from blocking content, throttling or slowing connections and offering preferential treatment through paid prioritization.

If the senators are able to sway a single Republican, they will have the votes needed to ensure the 2015 rules remain in place. A CRA requires a simple majority to pass and cannot be blocked by filibuster.

Even with half of the Senate on board with the bill, finding the final vote is likely to prove difficult. Susan Collins has been a swing vote since the start of the Trump administration and her decision to sign on with the bill continues her reputation for crossing party lines, but some of her fellow defectors may prove harder to convince.

Senator John McCain, R-Az., is typically considered a possible swing vote on many issues but net neutrality is not one of them. The 81-year-old senator has consistently opposed the FCC’s attempts to classify broadband internet as a public utility and would likely not join an effort to protect those rules.

McCain’s fellow representative from Arizona Jeff Flake has also regularly acted as a dissenting voice against the policies of President Donald Trump, but is also unlikely to flip. He publicly supported the current FCC’s decision to undo net neutrality protections. Flake also proposed a CRA of his own last year that killed another FCC policy—the Broadband Consumer Privacy Rules, which prohibited ISPs from collecting information about users without explicit permission.

There were two Republican senators who did not vote for Flake’s CRA on the Broadband Consumer Privacy Rules: John Isakson, R-Ga., and Rand Paul, R-Ky.

Isakson did not support the FCC’s net neutrality rules in 2015 and continued to oppose them as recently as last year and is unlikely to flip. Rand Paul has likewise consistently opposed net neutrality and last year signed on to a Senate bill that would have done away with the protections put in place by the FCC under the previous administration.

There is one likely target within the Republican caucus who may provide the one remaining vote required. Senator John Kennedy, R-La., is reportedly considering the proposal and has expressed support for finding a legislative solution to establish net neutrality protections.

If Kennedy or another Republican chooses to join the group of 50 set to support the bill, it will begin the ball rolling on an attempt to stop the FCC’s decision to roll back net neutrality protections.

The fight would then move to the House of Representatives, where Republicans hold a 40-seat advantage. A handful of Republican members of Congress were vocal opponents of the FCC’s vote last month, but finding votes would likely be a challenge.

Even if the CRA were to successfully pass in both chambers, it would face a final challenge at the desk of President Donald Trump, who would likely veto the motion.