Indy car racing had a split about a decade ago after various team owners and Indy track owner Tony George disagreed on the future of the series. Tony George formed IRL, a series that was all oval, and featured primarily American drivers. The rival owners formed CART, which had a mix of oval, road race and street courses, with a lot of international drivers.
For the first few years CART was cleaning IRL's clock, but the last five years has seen a definite shift, with IRL clearly being the front runner in this silly war. IRL has since added a few road courses to it's schedule, while CART survivied near-bankruptcy just over a year ago and is now known as Champ Car, with no ovals on the schedule. However it's meant that open wheel racing, which just a decade ago was the premier form of racing in the US, has fallen almost off the map in terms of mainstream attention, with only the Indy 500 race getting any real coverage. NASCAR has of course taken advantage of this fuckup big time, and it's a big reason why they've been allowed to become as big as they are.
Fans like me hope that IRL and Champ can reuninte soon and get back to building up open wheel as a strong alternative to NASCAR, but there's too many egos involved on both sides at present to allow that to happen.
:lol