Senate Democrats who are trying to force a vote on reinstating net neutrality rules have hit a key milestone.

A Congressional Review Act (CRA) resolution that would reverse the Federal Communications Commission's net neutrality repeal needed 30 co-sponsors in order to get a Senate vote. Today, Sen. Claire McCaskill (D-Mo.) announced that she has signed on to be the 30th co-sponsor.

30 is the magic number of cosponsors needed to get a #NetNeutrality vote in the full Senate. Proud to be that 30th cosponsor of @SenMarkey bill to restore free and open internet. — Claire McCaskill (@clairecmc) January 8, 2018

Sen. Ed Markey (D-Mass.) announced the CRA resolution shortly after the FCC's repeal vote last month. All 30 supporters are members of the Democratic caucus.

"[W]e now have the 30 votes we need to force a vote on my CRA to reverse the repeal of #NetNeutrality," Markey wrote on Twitter today.

A big step toward restoring a free and open Internet: with the support of @clairecmc, we now have the 30 votes we need to force a vote on my CRA to reverse the repeal of #NetNeutrality! pic.twitter.com/gXtWQmeIJS — Ed Markey (@SenMarkey) January 8, 2018

Markey's bill likely won't restore the net neutrality rules in the end, even if it passes in the Senate. Forcing a vote will be more difficult in the House, where Republicans hold a larger majority. Even if the bill passes both the Senate and House, President Trump is likely to issue a veto in order to let the FCC's net neutrality repeal go forward.

Still, Markey's resolution could pass in the Senate if all Democrats and two Republicans vote in favor of it. A vote would keep net neutrality in the spotlight as Democrats prepare to make the repeal a campaign issue in the November elections.

Democrats haven't said when they will try to force a vote on Markey's resolution, but US Senate Minority Leader Chuck Schumer (D-N.Y.) has promised to make it happen. Last month, noting that legislation to reverse the repeal "doesn't need the support of the majority leader," Schumer said, "there will be a vote."

The Congressional Review Act is the same mechanism used by Republicans last year when they eliminated FCC rules that would have protected broadband customers' online privacy.