In a midnight session almost six years ago, then-Senator Barack Obama voted to gut a guest-worker program that sponsors of an immigration bill considered vital to their effort to legalize millions of undocumented residents.

A few weeks later, the bipartisan measure was dead -- blocked from a final vote by Republicans who called it amnesty for lawbreakers and Democrats who said it would hurt American workers and treat immigrants unfairly.

The failure of the 2007 effort illustrates the importance of an agreement announced yesterday by business and labor leaders on principles for a new visa program for low-skilled immigrants. Opposition to that one plank helped kill President George W. Bush’s attempt to revise immigration laws, and it could do the same to Obama’s campaign to grant legal status to 11 million undocumented people living in the U.S.

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