By a single vote, Senate Republicans on Wednesday blocked an expansive fiscal stimulus package championed by Democrats, as partisan rancor engulfed the effort to inject a quick burst of spending into the slowing economy.

The package needed 60 votes under Senate rules to move forward but failed 58 to 41, with 8 Republicans joining 48 Democrats and 2 independents in support of it. The majority leader, Senator Harry Reid of Nevada, switched his vote to no from yes at the last second, a parliamentary move that lets him control the next steps on the bill.

The political brinkmanship in the Senate stood in marked contrast to the House, where Republicans and Democrats led by Speaker Nancy Pelosi took just a week to reach a deal on an economic stimulus package with President Bush, and just four more days to pass the bill.

The measure was opposed by Republican leaders who said the Democrats added too many costly provisions, including an extension of unemployment benefits, tax credits for the coal industry and increased subsidies for home energy costs.

The total cost of the Senate plan came to about $204 billion over two years, or about $40 billion more than the House version.

Senator Mitch McConnell of Kentucky, the Republican leader, had called for the Senate simply to adopt the House package with two changes: payments for Social Security recipients and disabled veterans, and a stipulation that illegal immigrant workers not receive payments. Mr. McConnell renewed that demand on the Senate floor just before the vote and chided the Democrats.

Praising House Democrats and Republicans for their stimulus deal, Mr. McConnell said, “Then, in an apparent jolt of nostalgia for last year, Senate Democrats decided to co-opt a bipartisan proposal produced by the House to put together a carefully crafted political document.”

Aides to Mr. McCain said that he would have sided with the Republican leaders and that his vote was not needed.