Hypothetical: Clarence Thomas leaves the USSC (for whatever reason). Who should replace him?

[YoungDemCA]

In this 2016 hypothetical/scenario, Democrats win both the White House and the Senate (the latter with plenty of seats to spare), and let's say at least come close to winning the House of Representatives - just for the sake of argument.

For whatever reason (say, an unexpected illness, or the Senate finally having the wherewithal and votes to impeach Thomas on charges involving his failure to report his wife's income- income which came from right-wing activist organizations), Clarence Thomas leaves the Supreme Court in early 2017. (And there was much rejoicing.. )

Now, imagine that you are a senior adviser to the new Democratic President. Keeping in mind the symbolism of having at least one "African-American seat" on the Court - with liberal icon Thurgood Marshall being there before Thomas, and both of them being black men - who would be your preferred nominee, that would replace Thomas?