The Senate drove a stake Thursday through President George W. Bush's plan to legalize millions of unlawful immigrants, likely postponing major action on immigration until after the 2008 elections. The bill's supporters fell 14 votes short of the 60 needed to limit debate and clear the way for final passage of the legislation, which critics assailed as offering amnesty to illegal immigrants. The vote was 46 to 53 in favor of limiting the debate. Senators in both parties said the issue is so volatile that Congress is highly unlikely to revisit it this fall or next year, when the presidential election will increasingly dominate American politics. A similar effort collapsed in the Congress last year, and the House has not bothered with an immigration bill this year, awaiting Senate action.