BANGALORE, India — Lawmakers cleared the way Wednesday for India to forge a single common market out of its tangle of overlapping federal and state taxes, a step analysts describe as the most important economic change in more than two decades.

The vote by the upper house of India’s Parliament was cheered by supporters of Prime Minister Narendra Modi, who is seeking to build a legacy as an economic modernizer. Though he won a landslide victory in the 2014 elections, he has struggled to marshal parliamentary support to push through his major economic initiatives.

The protracted battle over the tax measure — a constitutional amendment to introduce a single national goods and services tax — came to embody the zero-sum political atmosphere in New Delhi. Though economists forecast that the new tax system could increase India’s growth rate by as much as 2 percentage points, it was blocked in Parliament for years by whichever main party was in opposition.

As the logjam gave way this week, analysts said they hoped the goods and services tax would both yield more revenue and be less burdensome.

New York Times