WASHINGTON — Stung by revelations that his plan would cut spending less than advertised, House Speaker John Boehner on Tuesday postponed a vote on a debt-ceiling measure that was already running into opposition from Tea Party conservatives. The move came just a week before an Aug. 2 deadline for staving off the potential financial chaos of the nation’s first-ever default.With time running short, the speaker promised to quickly rewrite his debt-ceiling legislation after budget officials said it would cut spending by less than $1 trillion over the coming decade instead of the promised $1.2 trillion. The vote originally scheduled for Wednesday is now set for Thursday. That may give Boehner more time to hunt for votes, but it gives Congress and the White House even less time for maneuvering.Meanwhile, public head-butting between Democratic President Barack Obama and the Republicans showed no sign of easing. The White House declared Obama would veto the Boehner bill, even if it somehow got through the House and the Democratic-controlled Senate.For all that, it was the Tea Party-backed members of Boehner’s own party who continued to vex him and heavily influence the debt and deficit negotiating terms — not to mention his chances of holding on to the speakership.Their adamant opposition to any tax increases forced Boehner to back away from a “grand bargain” with Obama that might have made dramatic cuts in government spending. Yet when Boehner turned this week to a more modest cost-cutting plan, with no tax increases, many conservatives balked again. They said the proposal lacked the more potent tools they seek, such as a constitutional mandate for balanced budgets.