Pure electric and plug-in hybrid conversions have been around a long time, though the total number of them on roads has not been tracked. CalCars, a California non-profit organization, has been pushing for tax credits and other incentives for years, for example, and the Electric Auto Association has been around since 1967. There are plenty of EAA members who have converted their own cars and motorcycles to run on battery power, because for most of the years since 1967, it wasn't possible to buy a plug-in car. Even today, consumers can become "do-it-yourselfers" with conversion kits they purchase and do in their own garage, or they can take their car to an established conversion vendor.
While the Federal government should continue providing Qualified Plug-in Electric Drive Motor Vehicles (IRC 30D) tax incentives for new plug-in vehicles, they should extend the same incentives to EV / plug-in conversions. Conversions target 250M existing vehicles on the roads, can save over 40% of fuel use or no fuel at all, have a smaller carbon footprint than new car since they reuse most of the original vehicle, and cost less to buy as an incremental expense making plug-in more affordable.
If you ask representatives of major automakers about conversions, the conversation becomes a bit stifled and awkward. Besides the competitive issues at stake, they also express concern about whether it's a good idea to support conversions unless they follow strict OEM guidelines, government mandates, and inspections. Then there are the concerns about potential negative publicity or recalls, should something go seriously wrong with a converted EV. It's likely the White House will have similar trepidations.
Nonetheless, the group is looking for 25,000 signatures in order to have the EV conversion petition considered by the White House. As of press time, the number was under 300.