A study of 150,000 Florida felons given the right to vote found:
"One thing that limits the electoral impact of restoring ex-felons’  voting rights is that they turn out at particularly low rates. To  demonstrate this, we first look to the population of ex-felons who were  restored the right to vote under Crist and calculate what share voted in  2016. 
We find that just 16 percent of black and 12 percent of nonblack  ex-felons voted. (We defined nonblack as white, Hispanic, Asian, and  other due to data limitations.)"
"The potential electoral impact of Florida’s ballot initiative is further  limited by the fact that the ex-felons who do vote are not politically  uniform. While black voters within this population overwhelmingly  register with the Democratic Party (87 percent), nonblack voters within  this population were more likely to register as Republicans (40 percent)  than as a Democrats (34 percent). The fact that 26 percent of the  remaining nonblack voters affiliate with neither party suggests that  their votes may not reliably be cast for either party."
https://www.vox.com/the-big-idea/2018/11/2/18049510/felon-voting-rights-amendment-4-florida