Senate Democrats have added language to the annual defense authorization bill to require women to register for the draft, prompting a backlash from Republicans and social conservatives and complicating the chances of moving the bill on the Senate floor before Election Day.

Conservatives led by Sen. Roger Wicker (R-Miss.) are certain to attempt to remove the provision requiring women to register for the draft, which could present a tough vote for Sens. Jon Tester (D-Mont.) and Jacky Rosen (D-Nev.) and other Democrats in tight reelection races.

But Senate Armed Services Committee Chair Jack Reed (D-R.I.) defended the proposed policy change, arguing that women can hold many warfighting positions without serving as front-line infantry troops.

Senate aides point out the issue cuts across party lines, with some Republicans generally supportive of requiring women to sign up for the Selective Service System, just like men when they turn 18.

Senate Republicans are already raising doubts about whether Senate Majority Leader Chuck Schumer (D-N.Y.) will even bring the bill to the floor anytime soon, given the dwindling number of days on the legislative calendar before the election.

Voting to require women to make themselves eligible for the draft could come back to bite Democrats in Republican-leaning or battleground states, such as Montana and Nevada.