Reid told reporters that once two amendments on each side had been voted on Wednesday, he and McConnell would “have a piece of legislation” that he believes will pass.

The stated goal of a bipartisan Senate supplemental signals that no troop withdrawal dates will make it onto the bill heading into conference with the House. Withdrawal provisions would likely prevent McConnell and Republicans from backing the supplemental even as a placeholder.

Aiming to give Democrats a chance to air their views on the war, Reid initiated votes on two Iraq options that will be procedurally removed from the water-resources bill before its final passage. The first option adds waivers to the Senate’s first supplemental spending bill, and the second calls for most troops to leave Iraq within a year.

Sen. Chris Dodd (D-Conn.), a cosponsor of the stronger second option, has challenged his Democratic White House rivals to join him. Sen. Barack Obama (D-Ill.) answered the call Tuesday, announcing he would vote for both Iraq measures as a way of warning the Iraq government — not because he supports the stronger option.