1. Kerik was a big mistake.
2. He was too ill to run.
3. New York City's economy would collapse without the illegals. That doesn't mean Rudy is in favor of open borders, but it probably means he would favor amnesty (or "comprehensive immigration reform," as the Dems like to say). He certainly wouldn't favor everyone reporting them when they're discovered.
Rudy was NOT too sick last year nor does our economy need most of the illegals, many of whom are violent and gang members. In New York the Russian Mafia has established itself quite well.