The passage of S. 3709, the enabling legislation that facilitates the Indo-US civilian nuclear cooperation agreement, by an overwhelming 85-12 margin (with three abstentions), is being widely hailed as a triumph of bipartisanship.

Curiously, however, the vote on the 'killer amendment' indicated that party lines were not that easily blurred.

Senator Barbara Boxer (Democrat, California) had during the Senate debate on the nuclear deal introduced amendment 5187, which made the deal contingent on the President of the United States 'certifying that India had agreed to suspend military-to-military cooperation with Iran, including training exercises, until such time as Iran is no longer designated as a state sponsor of terrorism'.

In the run up to the vote, the government of India had repeatedly said any attempt to link the nuclear deal with Iran would be a surefire deal-breaker; the Bush Administration and its pointman on the deal, Under Secretary of State for Political Affairs Robert Burns, had reinforced that message while warning the Senate against any attempt to impose such conditionalities on the deal.

Boxer's amendment, thus, was seen as certain to pull the plug on the deal - and when it came up for vote, it lost by a margin of 59-38 with three Senators abstaining.

The narrowness of the margin is in stark contrast to the overwhelming final vote in favor of S.3709 - and a breakdown reveals an interesting story: Democrats by far outnumbered Republicans in supporting the killer amendment.

29 Democrats (including the likes of Barak Obama and Hillary Clinton) voted in favor, against just nine Republicans. Conversely, of the 59 votes cast against the amendment, 44 were by Republicans, with only 15 Democrats voting to kill the Boxer deal-breaker.

The final vote on S 3709, however, saw party lines blurring, though the Republicans again outvoted Democrats: Of the 85 votes in favor, 53 were by Republican Senators against 32 by Democrats (two Republicans and one Independent abstained).

Significantly, all 12 votes cast against the Indo-US nuclear bill were by Democrats - no Republican voted against a bill that has been seen as a cornerstone of President George W Bush's [Images] foreign policy.