The historic Senate vote on immigration fell a bit short of the 70 votes supporters hoped for. But a two-to-one margin in the final 68-32 margin is still an accomplishment in a body that rarely sees controversial measures pass. And it's even more remarkable when compared to the 2010 Senate vote on the DREAM Act.

Admittedly, the DREAM Act was a much more liberal piece of policy. The bill voted on Thursday afternoon was intentionally crafted by eight senators from both parties to have broader appeal. To that end it was largely, but not entirely, successful. Seventy-three senators voted on both the DREAM Act and the new immigration measure. Of those, the vast majority voted the exact same way both times, either in opposition or in support. Where senators changed votes, though, is telling.

This chart shows those 73 senators' votes, plotted on a grid. The upper left corner is those who supported both measures; lower right, those who opposed both. What's interesting is the other two boxes. In the upper right box are all of the senators who opposed today's measure but supported the DREAM Act — precisely none of them. The other box is the reverse, those who opposed the DREAM Act but voted "yes" today.

Those switched votes aren't the only thing that made a difference, however. The chart below shows votes from senators who only voted on one of the two bills — either because they left office or only came into office between the two votes. The two lefthand clusters below are votes for and against the DREAM Act; the two on the right are votes for and against today's bill.

It's immediately clear that today's vote had much more support from both parties among the new senators. Every Democrat voted for it, and far more Republicans did than voted only for the DREAM Act.

Again: today's success wasn't only due to a change of heart on the part of those twelve senators in that lower lefthand box. It's a much more moderate bill, one aimed at enticing the House to lend its support. How that vote will play out is much harder to calculate.

Photo: Senators McCain and Schumer celebrate. (AP)