WASHINGTON — An $838 billion economic stimulus bill backed by the White House narrowly advanced in the Senate yesterday over strong Republican opposition. The vote was 61-36, one more than the 60 needed to move forward. Democratic leaders promise to deliver the emergency legislation to President Barack Obama for his signature in a few days, after the House negotiates a final compromise on the bill.The Senate vote was close, but Republican Sens. Susan Collins and Olympia Snowe of Maine and Arlen Specter of Pennsylvania broke ranks to cast their votes to progress the bill once the White House and Democratic leaders agreed to trim about $100 billion on Friday.Just before yesterday’s vote, Republican opponents attacked it as too costly and unlikely to have the desired effect on the economy. All 36 votes in opposition were cast by Republicans.The two remaining versions of the legislation are similar — $838 billion in the Senate and $819 billion in the House — but the measure nearing approval in the Senate calls for more tax cuts and less spending than the House bill, largely because it includes a $70 billion provision to protect middle-class taxpayers from falling victim to the alternative minimum tax.