WASHINGTON — It has been labeled a tax grab and a bureaucratic nightmare by conservative antitax activists, an infringement on states’ rights and a federal encroachment on the almost-sacred ground of Internet commerce.

Yet legislation to help states force online retailers to collect sales taxes easily cleared its first procedural hurdle on Monday evening, and even its fiercest opponents are looking to the House for a last stand. The Senate voted 74-20 to take up the legislation for debate and amendment.

“I’m not above believing in miracles,” said Dan Holler, a spokesman for Heritage Action, the activist arm of the conservative Heritage Foundation, which has made opposition to the Internet tax bill a “key vote” — so far with little impact.

The bill, known as the Marketplace Fairness Act, is that rare piece of legislation that has turned Democrat against Democrat, Republican against Republican and business against business, while uniting states as different as New Hampshire, Montana and Oregon — which have no sales taxes — against virtually every other state.