Obama refuses to endorse Sanders or Clinton. Is that normal?

President Obama says he won't endorse a presidential candidate until after the primaries. While Obama has plenty of precedent for his decision, pundits and public alike can't help but speculate. 

President Barack Obama will not publicly support a presidential candidate until after the primaries, White House chief of staff Denis McDonough told Chuck Todd on NBC's "Meet the Press" Sunday. 

It is unusual, and perhaps unbecoming, for a sitting president to endorse a candidate from his own party before the primaries, particularly when the outcome remains in doubt: According to recent poll aggregation by Real Clear Politics, Sanders is beating Clinton in New Hampshire, 50 percent to 46 percent. But Clinton is ahead of Sanders in Iowa, 48 percent to 45 percent. 

In a New York Times op-ed Thursday, Mr. Obama offered what some see an additional reason for his reluctance to back a candidate: Gun control. 

“I will not campaign for, vote for or support any candidate, even in my own party, who does not support common-sense gun reform,” wrote the president.

And when asked if Senator Sanders’ gun policy warrants executive approval, McDonough said Obama’s statement doesn’t exclusively apply to the presidential primary – it extends into all upcoming elections, be it presidential, congressional, or gubernatorial. 

“At least he will see who the nominee is at the end of [the primary], that’s not our job,” says McDonough. “That’s the job of the party to make those decisions and then they’ll take a look at the agendas and the positions of those candidates, then we’ll make some final decisions.” 

Mr. Todd then specifically asks McDonough if Obama’s withheld support can be attributed to the issue of gun control.

“No,” responds McDonough, “the President is saying that across the board he’s going to be a single issue voter on this. He thinks that makes sense, given the enormity of the challenge. 30,000 deaths a year.” 

And regardless of Obama’s unprecedented position as a single-issue voter on gun control, his chief of staff says the president will follow protocol. 

“We’ll do exactly what has been done in the past, which is when the nominee is set, then the President will be out there,” said McDonough. 

Despite pundits’ persistent urging, a public pre-primary announcement of support by the sitting president would be uncommon. 

Ronald Reagan waited to endorse George H.W. Bush until May 1988 and George W. Bush waited to endorse Sen. John McCain until March 2008. 

Sitting president Bill Clinton did endorse his vice president, Al Gore, for president in December 1999 before the January Iowa caucus or February New Hampshire primary, but that announcement was not as consequential, considering their relationship between Gore and Clinton as well as Gore’s lack of competitors. 

So far in the presidential race, Obama has offered praise to both Clinton and Sanders while staying neutral. 

“I think Bernie is capturing a sense among the American people that they want to know the government’s on their side…And I think that is incredibly important,” Obama told ABC’s George Stephanopoulos during a November interview. And in April 2015 before Sanders’ even announced his campaign for presidency, Obama said Clinton “would be an excellent president.”

But the president has suggested that we shouldn't read too much into his kind words.

“I’m not going to make endorsements,” Obama told Mr. Stephanopoulos in November. “It’s important for the process to play itself out.”

Both Sanders and Clinton rallied supporters for gun control in recent weeks, better aligning themselves with the president's perspective and potentially making themselves candidates for Obama's approval.