Recreational vehicle retailers from across the country were sipping morning coffee at a convention in Las Vegas earlier this month when word whipped through the hotel's "dealers' lounge" that the U.S. Congress was considering tax law changes threatening their businesses.

Republicans in the House of Representatives wanted to jettison a part of the tax code that lets dealers of RVs, cars, boats, even farm and construction machinery, write off all the interest expense of keeping inventories of vehicles on their sales lots.

The RV dealers jumped on the phones to their representatives in Washington, adding to a wave of calls made by members of the powerful National Automobile Dealers Association (NADA) as well lobbyists for boat dealers and farm machinery dealers.