Following the departure of a number of top teams and engine manufacturers to the rival Indy Racing League (IRL), CART declared bankruptcy after the 2003 season.

Champ Car was able to maintain a full field and most of CART's street circuit sanctioning agreements for 2004.

Both Champ Car and the IRL continued to suffer from reduced fields, sponsorship, and television ratings.

Merger talks in 2006 were halted after disagreements regarding Champ Car's upcoming Panoz chassis and leaked details of a shared new series upset IMS.

[2] After successful merger negotiations, in mid-February 2008, Champ Car authorized bankruptcy to facilitate a February 22 agreement in principle to merge with the IRL.