WASHINGTON — FCC Chairman Ajit Pai and two other Republican commissioners are expected to vote to repeal most of the agency’s net neutrality rules on Thursday, but they will experience protest, rancor, and pressure in the hours leading up to the decision.

What is less certain is what happens next, and if the issue of net neutrality in any way becomes an issue headed into the 2018 midterm elections.

On Tuesday, nearly 37 Senate Democrats and two independents sent a letter to Pai, urging him to abandon the proposal, which they called a “stunning regulatory overreach.”

“The future of the internet hangs in the balance,” they wrote.

A Republican member of Congress, Rep. Mike Coffman of Colorado, also sent a letter, urging him to delay the vote and expressing concern of “unanticipated negative consequences.”

On the Senate floor, Sen. John Thune (R-S.D.), the chairman of the Senate Commerce Committee, expressed his support for Pai’s proposal, but also again called for Democrats to come to the table and work out a compromise.

“True supporters of an open internet should be demanding such legislative protections today — not posturing while waiting for years during protracted legal proceedings or waiting for the political winds to turn,” he said.

Pai is proposing to eliminate rules that require that internet providers treat content traffic equally. The regulations ban ISPs from blocking or throttling content, or from selling “fast lanes” so content companies can reach consumers faster than non-paying sites. ISPs still would have to disclose the way that they handle internet traffic, but the FCC would have a reduced oversight role.

The Pai proposal would reverse the rules that have been in place since 2015, when the Obama-era FCC was controlled by Democrats. Back then, Thune floated a compromise proposal that would ban blocking and throttling and so called paid prioritization, but Democrats were wary of it as it would have stripped the FCC of much of its authority.

Now, there is still little movement for legislation, and it’s likely that Pai’s proposal will head to court — which has been the fate of all past efforts at net neutrality. A Morning Consult poll late last month showed that 52% of respondents support the current rules, including 55% of Democrats and 53% of Republicans. Support, however, has fallen since the summer.

Democrats and the collection of public interest and consumer groups, online activists, and other organizations have spent the past few days calling attention to the pending action, even as industry trade groups argue that they are vastly overstating the impact of the proposal. In an interview on Monday, Pai even called some of the warnings, including those coming from celebrities like Alyssa Milano, “hysteria.”

He again argued that the current rules are so onerous that they are stifling investment, and FCC officials on Tuesday pointed to the support for his proposal coming from small and rural broadband providers.

For the foreseeable future, though, this once wonkish policy debate will be the source of calls for action and cries of alarm.

On Tuesday, net neutrality activists staged “Break the Internet” day, with participation from sites like Reddit, Mozilla, and Tumblr, while a group of internet pioneers, like Tim Berners-Lee and Vinton Cerf, sent a letter to congressional leaders calling on the vote to be canceled. A number of non-profits and religious groups, including the U.S. Conference of Catholic Bishops, have called on the FCC to retain the rules.

Rep. Ro Khanna (D-Calif.), Rep. Maxine Waters (D-Calif.), and Rep. Keith Ellison (D-Minn.) are among those expected to speak outside of the FCC offices on Thursday.