Let's see. Slavery, to me, is a state of servitude to a single master, and that servitude is expected, if not demanded, regardless of the reasonableness, humanity, and intelligence of the sundry duties which characterize bondage.
Slavery exists when one is required to perform, act, think, and indeed exist under a set of rules, expectations, and institutions that are exclusively of the slavemaster's design. While enthusiasm for the master's plan isn't compulsory, it certainly helps it all go down better. Slavery is also characterized by the extreme consequences of open dissent or attempted escape.
Under that admittedly broad definition, liberals are already enslaved, but the slavemaster currently occupies the White House, and the DUmmies are furiously planning for the coronation of their next slavemaster.