President Barack Obama is proving to be the exception to the political rule of staying out of closely contested primary races.

The Monday endorsement of U.S. Sen. Brian Schatz over U.S. Rep. Colleen Hanabusa in the coming Democratic primary shows that Obama is not afraid of picking one Democrat over another.

"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. "There is no question that Sen. Schatz is the right choice to continue delivering for Hawaii."

On one level, voters in Hawaii who keep score will know that Obama is also keeping score.

Early in the 2008 primary, Schatz jumped out to lead the local Obama campaign. It was a smart move as Obama proved to be Hawaii’s favorite, favorite son.

The cheering, however, stopped at the door to the late iconic Hawaii U.S. Sen. Daniel K. Inouye’s office. He knew Obama in the Senate and thought New York U.S. Sen. Hillary Clinton would be a better president.

So Inouye endorsed Clinton and asked Hanabusa to lead the Hawaii for Clinton campaign. So this isn’t the first gun fight for Hanabusa and Schatz.

This kind of history is why Democrats so need a unity breakfast after their primary elections.

What do the involved parties get out of the endorsement?

Obama shows that he backs incumbents, which is the kind of principle that all 100 members of the U.S. Senate know and appreciate.

Already this year Obama has endorsed three incumbent Democrats who are facing primary challenges.

He endorsed Gov. Neil Abercrombie, an old family friend, even as Abercrombie faces state Sen. David Ige in our local primary race.

In Louisiana, the president endorsed Mitch Landrieu’s reelection as mayor of New Orleans, but interestingly, has held off on U.S. Sen. Mary Landrieu, Mitch’s sister, because support from Obama outside of strongly Democratic New Orleans is seen as a minus in the conservative Bayou State.

In Hawaii, the state is still in love with Obama, although you could take "madly" and "unquestioningly" off the list of ways to describe Hawaii’s affection.

In May 2011, the statewide poll taken by this paper and Hawaii News Now had 74 percent of the voters approving Obama’s job performance.

In February of this year, the poll had Obama at 67 percent.

Some of that is because there is now open concern that his health insurance plan wastes money and doesn’t do anything that Hawaii’s own prepaid health care plans didn’t already do — but more about that in future columns.

For Schatz there is some immediate help: fundraising.

March 31 was the last day to contribute for donations to be reported for the quarter. The endorsement should mean a bit of a mainland money bump for Schatz, who is already leading Hanabusa in dialing for dollars.

For the campaign, there is some help, but probably not much, according to a quick survey I did among political veterans around the state Capitol.

"It will help with the true-believer Obama people, but that is about all," said one long-time Democratic representative.

"Maybe with some undecided voters, but most endorsements like that don’t do much," said a veteran campaign consultant.

The other obvious thing the endorsement should do is heat up the fire in the Hanabusa campaign, which so far has been simmering, not boiling.

Richard Borreca writes on politics on Sundays, Tuesdays and Fridays. Reach him at rborreca@staradvertiser.com.