Obama’s proposal would have also heaped an extra $173 billion in interest expenses on state and local governments over the last decade, the study found.

{mosads}Backers of the exemption, like the mayors group, say they remain highly concerned it would be targeted in a rewrite of the tax code or a big deficit deal. Supporters say the exemption helps fund a wide range of projects, like schools, roads and hospitals.

The new study also notes that “the American Society of Civil Engineers recently gave a D+ grade to US infrastructure.”