The proposal would boost consumer tax credits to as much as $12,500 for EVs assembled in a factory represented by unions with U.S.- produced batteries.

The ad is asking Congress to "put politics aside" and apply the EV tax credit equally to all electric vehicles assembled by U.S. auto workers.

What appeared to be a path forward on EV tax credits at first glance evolved into a last-minute scramble, as automakers and some Senate Democrats seek changes to the provision's strict battery content and assembly rules, which they said could delay vehicle eligibility.