Yes, of course he has a chance, and a fairly good one at that. But it's not as good as it was in 2012, when the only time his nomination was ever really in doubt was Rick Perry's entrance. Yes, I know Cain/Gingrich/Santorum led in the polls at various points, but I don't think many people actually expected that to hold.
I would argue the last best opportunity to take Mitt Romney out was the Florida primary. After that, Newt teetered, and Santorum (who basically is the inverse of Romney, totally unable to appeal to Republicans who vote primarily on economic issues) became the new anti-Romney. Santorum had no ability to win, Newt might have at least had like a 1 in 50 shot.