Multiple news sources are reporting that South Carolina Senator Tim Scott will endorse Rubio shortly. That has to be good news for Rubio in South Carolina. Scott is close to Rubio, but the Cruz campaign has reportedly been lobbying him to stay neutral.
Rubio still needs to get through the wringer of New Hampshire before we can assess his prospects in South Carolina, and leaking this now may be a way to ensure Rubio gets some momentum regardless of where he finishes in Iowa. But the Rubio camp has to be very happy right now.