Schatz, who was appointed to the Senate in late 2012, is facing a tough primary challenge from Rep. Colleen Hanabusa (D-Hawaii). Public polling has shown the primary is a dead heat.
He has deep ties to Obama — Schatz chaired Obama's 2008 presidential campaign in Hawaii, and some of his staff are former Obama aides.
Obama's endorsement could be a major development for Schatz in the race. The president remains very popular in his home state, where he won 71 percent of the vote in 2012.