President Obama is endorsing Sen. Brian SchatzBrian Emanuel SchatzQuestions loom over Franken ethics probe 200 nations plan 2018 talks to keep Paris Agreement momentum Democrats scramble to contain Franken fallout  MORE (D-Hawaii), giving him a potentially big boost in his Democratic primary.

"Brian's deep commitment to the people of Hawaii and his effective leadership are why I believe it is important to return him to the Senate," Obama said in a statement released by Schatz's campaign. "Senator Schatz is protecting Hawaii's values and fighting every day on behalf of middle-class families.  There is no question that Senator Schatz is the right choice to continue delivering for Hawaii."

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.