While the article says that Joe Donnelly (D-IN) is expected to vote for it, I could see him wavering if enough pressure is applied. Donnelly has not, as far as I know, publicly committed to UBC's one way or the other aside from his vote to proceed on debating the bill. Donnelly very narrowly won election last year largely because his opponent, Richard Mourdock, had a very public gaffe about rape and abortion.
Indiana is a very conservative and gun-friendly state and a vote for gun control would very likely hurt Donnelly's chances of re-election (his seat was previously occupied by Republican Dick Lugar who lost the 2012 Republican primary due to his lack of conservatism). It is also worthy of note that Sen. Dan Coats (R-IN) who is a well-known moderate that, in years past, would have likely supported this bill, has come under enough political pressure to oppose it and vote with the Republican filibuster against it.
I've written Donnelly several times since Sandy Hook and after about two months, he finally sent me a reply stating that he opposed an AWB. This leaves me with the impression that Donnelly is hesitant to commit to anything until he a gauge which way the political wind is blowing. Because of this, Indiana residents need to make sure that the political wind blows against S.649 and the Toomey-Manchin amendment.
Smith, and Wesson, and Me. -H. Callahan
Well waddaya know, one buwwet weft! -E. Fudd
All bad precedents begin as justifiable measures. -J. Caesar