Actually, this has been discussed here before.
AFAIK there’s no actual evidence that significant crossover registration occurred - the test would be to examine registration numbers in open primary states where there was not a strongly contested Republican primary, before and after operation CHAOS, and see if he could discern a consistent difference. But even then as complicated multiple factors were in play it would be hard to determine for certain that cause of any differences.
For what it’s worth, my guess is 1) that this was almost exclusively an intramural affair between the Democratic candidates and that CHAOS made little difference one way or the other and 2) on general principles it’s probably a good idea to avoid such efforts unless you can be reasonably certain of their outcome.
That’s my feeling. I don’t think, in the long run, it made a lot of difference in the Dem candidate. Obama was set up to win no matter what, and Hillary was actually blindsided by him and nothing could have helped her at that point. He was even more aggressive and corrupt than her own husband, which is saying a lot.
My only sense was that it distracted some GOPers from the important task of getting a good candidate of our own.