President Obama's endorsement on Monday of Sen. Brian Schatz (D-Hawaii) in a Democratic primary is a big deal.

Until now, Rep. Colleen Hanabusa (D-Hawaii) sported the most notable endorsement in the race: That of late senator Daniel Inouye (D), whose dying wish was for her to succeed him. But if there's one endorsement that could carry as much or more weight in what promises to be a contentious campaign, it's Obama's.

The broad unpopularity that has has turned Obama into a political albatross in many states does not extend to Hawaii, where he grew up and enjoys iconic status. Obama won 71 percent of the vote there in 2012. On average, 61 percent of Hawaii residents approved of the job he did in 2013, according to Gallup. Only in Washington, D.C. was he viewed in a better light.

"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," Obama said in a statement.

Picture the above quote in a 30-second TV ad. It would be a powerful message for Schatz, whose challenge is to prove to Democratic voters that he has used his time in the Senate wisely and can best represent the people of Hawaii in the years to come.

The race between Schatz and Hanabusa is rooted heavily in past rivalries and deeply personal divisions among Hawaii Democrats. Gov. Neil Abercrombie's (D) decision to appoint Schatz over Hanabusa was seen as an insult to the senator's legacy by many of his allies.

The president's endorsement of Schatz adds yet another blast from the past to the mix. Schatz endorsed Obama in the 2008 Democratic presidential primary. Inouye and Hanabusa backed Hillary Rodham Clinton.

Obama has also endorsed Abercrombie, who faces a contested primary. Obama appeared in a general election ad for Hanabusa in 2010, when she was a challenger trying to unseat a House Republican.

Rarely do endorsements move the needle in the campaigns. They are often overhyped and mean far less than the campaigns who tout them would lead you to believe. But this one matters for Schatz. Big time.