Bush, in an appearance Tuesday on MSNBC, was responding to questions about a passage in a book he has co-written with conservative lawyer Clint Bolick, in which he says undocumented immigrants should not be able to become citizens.
"A grant of citizenship is an undeserving reward for conduct that we cannot afford to encourage," Bush writes in "Immigration Wars: Forming an American Solution."
That's a reversal of position for Bush -- a conservative Republican whose wife is from Mexico, and who has generally held a position on the issue that more liberal that his party's -- The Miami Herald said.
As governor from 1999 to 2007, he supported legislation that would have allowed immigrants in the country illegally to get drivers' licenses. Last year he backed a route to citizenship for undocumented workers, and in 2007 he pushed an immigration reform bill supported by his brother, former U.S. President George W. Bush.
During an interview Tuesday on MSNBC, the former Florida governor said any reform should be "forward-leaning" but said he doubted Congress can craft a law that provides for a path to citizenship without encouraging illegal immigration.
"Going forward, if there is a difference, if you can craft that in law where you can have a path to citizenship where there isn't an incentive for people to come illegally, I'm for it," Bush said. "I don't have a problem with that. I don't see how you do it, but I'm not smart enough to figure out every aspect of a really complex law."
In their book, Jeb Bush and Bolick write that people should become eligible to earn permanent legal residency after being convicted and serving sentences for being in the country illegally.
"Such earned residency should entail paying taxes, learning English, and committing no substantial crimes," they say.
He and Bolick take issue with demands by some conservatives that border security must be tightened before they will support immigration reform. Such an attitude "is a good slogan but elusive on details and measurements," they say.
"What exactly is the magic moment we must wait for before we can fix the broken immigration system?" they ask.