Updated: 3:14 p.m.Senate Democrats who oppose a gun amendment to the defense authorization bill acknowledged Tuesday that it will be difficult for them to block the measure when it comes to the floor this week. “It’s going to be a tough vote, no doubt about it,— Democratic Conference Vice Chairman Charles Schumer (N.Y.), who threatened to filibuster the measure, said during a press conference Tuesday. The amendment by Republican Policy Committee Chairman John Thune (S.D.) would allow gun owners to carry concealed firearms into states with similar gun regulations. It will likely be considered on the floor Wednesday. Schumer said the measure “goes way beyond the legislation we’ve seen on the floor— relating to gun rights this year, including an amendment sponsored by Sen. Tom Coburn (R-Okla.) allowing guns on federal lands that was attached to legislation granting Congressional representation to the District of Columbia. Coburn’s amendment has all but killed the D.C. bill.While Schumer and Majority Whip Dick Durbin (D-Ill.) are rallying Members to vote against the Thune amendment, Majority Leader Harry Reid (D-Nev.) — who faces re-election in a state that favors broad gun rights — has kept a low profile on the issue. “He is anxious to not have this amendment show up at this time,— Sen. Frank Lautenberg (D-N.J.) told reporters. “He is definitely with us in the fear of the spread of concealed weapons. … The Majority Leader has built up an image of what he’d like to see, and that’s defeat this.— Reid said Tuesday he will vote for the Thune amendment.Democratic leaders are working to rally at least 41 Senators to vote against the amendment. Sen. Bob Menendez (D-N.J.) noted that he is telling Democratic colleagues to “look beyond this specific issue— when considering how to vote on Thune’s amendment. “If you go down this road, then you create a precedent,— Menendez said, noting that legislation chipping away at state control on other issues might prevail in the future. Sen. Ben Nelson (D-Neb.) said Tuesday that he will support the measure, which is co-sponsored by Democratic Sens. Mark Begich (Alaska), Max Baucus (Mont.) and Jon Tester (Mont.).Sen. Tom Carper (D-Del.) and Claire McCaskill (D-Mo.), two key moderates, have said they will vote against the amendment.