There is a group of conservatives in Florida who are starting an effort to recall Marco Rubio. Of course this is going nowhere but it does show Rubio has some repair work to do with his base both in Florida and around the country because of immigration.
Why this is especially problematic is that Rubio is also up for reelection in 2016. The last thing Rubio wants is a primary challenge. Imagine trying to do with the headache of someone in your home state saying you’re too liberal while you around the country saying you’re the voice of a new conservatism.
From a tactical point of view, if a challenge is anything approaching serious Rubio will have to divert the key resources of time and money to deal with it. Those are both things any campaign has in short supply so anything that takes his focus off the early primary/caucus states could critical.