I recall reading that the 9th AF had great hopes for the A-26 in the CAS role. It could carry a lot more ordnance than the P-51, P-47 or P-38.
Tests showed that at low altitude an A-26 was just as fast as a P-47. But the A-26 proved to be a much larger target and much more easily hit by antiaircraft fire than was the P-47.