Conversation so far:
what did Chris Christie do on the trump campaign?
Despite having criticized Donald Trump prior to leaving the race, he endorsed Trump on February 26, 2016.
what were Chris Christie responsibiliites on the trump campaign?
On May 9, 2016, Trump named Christie to head a transition team in the event of a Trump presidency.

Question: what was his administration role?
Self-contained rewrite: what was Chris Christie's Trump administration role?