WASHINGTON - The Senate voted yesterday to block a looming tax increase averaging $2,000 for millions of taxpayers, after Senate Republicans succeeded in thwarting a Democratic plan to also raise taxes on investors.

The Senate bill, passed 88-5, provides a one-year fix for the alternative minimum tax but without matching the cost of the tax relief with new tax revenues. Without the fix, an estimated 25 million people would be subject to the higher AMT tax, up from 4 million in 2006.

The Senate vote puts it at odds with the House, where Democratic leaders, under a principle of not adding to the national debt, demanded that the AMT fix be paid for. Last month, the House passed legislation matching the AMT fix with about $80 billion in new tax revenues.

Senate Finance Committee Chairman Max Baucus, D-Mont., said it was not his first choice to pass an unpaid-for bill but "this is our best choice." He said 12 million people in the $100,000 to $200,000 income level alone would be hit by the AMT without the fix, and "we need to stop that from happening."

The bill now goes back to the House, where Rep. Charles Rangel, D-N.Y., chairman of the tax-writing Ways and Means Committee, suggested making up the difference by closing a loophole on offshore funds that now escape taxation.

Earlier yesterday, Senate Republicans united in stopping the Senate from moving to the House-passed bill. *