President Barack Obama has tried his best to be diplomatic about which candidate in the Democratic presidential primary he thinks hews closer to his agenda. But at a press conference on Tuesday, he tipped his hand a bit.

Speaking in southern California, Obama made the now-rote point that the differences between Hillary Clinton and Bernie Sanders are far narrower than those between Democrats and Republicans. But he added that he knows Clinton better (from her time as secretary of state) and suspects that "on certain issues, she agrees with me more than Bernie does."

Obama quickly noted that "there may be a couple of areas where Bernie agrees with me more." But it seemed more like an effort to prevent a bad headline than a full-throated endorsement.

And that gets to a larger point. Veterans of this White House don't feel particularly invested in boosting Sanders. They feel that way because the Vermont senator wasn't always there to boost them.

The latest evidence of that was passed along to The Huffington Post at the same time that Obama was speaking. It's a video from an April 2013 episode of "Real Time with Bill Maher" on which Sanders was a guest.

The topic turned to the economic recovery, which at the time remained relatively slow. Maher, however, was incredulous that Republicans (in this case, columnist Stephen Moore) were acting appalled after having been apologists for Obama's predecessor, George W. Bush.

Sanders agreed. But he wanted to burnish his credentials first.

"I'm not Obama's biggest fan," he explained. "I supported him, I'm an independent, but I'm critical of many aspects. When Obama came to office, there were 700,000 people a month who were losing their jobs. A month. So to say that 88,000 is not good, yeah, but compared to what."

This was not some new philosophical terrain for Sanders. He regularly argued that Obama didn't do enough to spur economic growth or address income inequality. And he has consistently argued that Obama was too keen on negotiating with Republicans when they were simply bad-faith negotiators.

The comment to Maher doesn't mean that Sanders was nothing but a critic of Obama. As Sanders' campaign spokesman Michael Briggs noted, the two have "worked together on many issues," including reforming veterans' health care and supporting community health centers. Obama campaigned for Sanders in 2006, and Sanders supported Obama after the primary season concluded in 2008 (as well as 2012).

"Bernie considers the president a good friend," said Briggs. "They've had differences, of course, but not nearly as many as Hillary Clinton had with Obama when she ran against him for president in 2008 and called Obama's foreign policy views 'naive.'" (The last point refers to Clinton's 2008 criticism of Obama's pledge to negotiate with America's enemies without preconditions.)

But it was the language that Sanders used to make his point to Maher -- "I'm not Obama's biggest fan" and "I'm critical of many aspects" -- that rankled White House aides. And in a Democratic primary where fidelity to Obama is proving to be a big asset, that is language that could come back to haunt him.