President Obama enthusiastically praised and championed Secretary of State Hillary Clinton in a joint interview Sunday night, sending what amounted to direct signals to his supporters that he would be pleased if she were his successor and that his supporters should forget any lingering tension from the hard-fought 2008 campaign, as the president himself has.

Obama and Clinton both sidestepped any questions about the 2016 campaign, and it remains unclear if Clinton will run again. But if she does, and wants to court the Democratic voters who backed Obama instead of her in 2008, the former first lady now has a very strong supporter for her credentials as a logical heir to Obama’s base: Obama himself.

“I just wanted to have a chance to publicly say thank you, because I think Hillary will go down as one of the finest secretary of states we’ve had. It has been a great collaboration over the last four years. I’m going to miss her,” Obama said in explaining why he had suggested a joint appearance with Clinton on 60 Minutes before the secretary of state’s tenure ends this week.

The president repeatedly spoke of Clinton’s service in the Cabinet in glowing terms, calling her one of his most important advisers. But just as importantly, he said what had at first been a marriage of political convenience turned into a genuine friendship.

“By the time Hillary joined the administration,I felt very confident and comfortable in our working relationship. I think what did evolve was a friendship as opposed to just a professional relationship,” the president said.

While the words the president said were important, it was even more significant that he chose to do the interview in the first place. The only other person Obama has done a joint interview with is his wife, Michelle. And it is almost unprecedented for a president to give a 30-minute interview solely to praise a member of his staff who is leaving.

To be sure, this was not an endorsement by Obama of Clinton’s 2016 presidential campaign. Many sitting presidents choose not to endorse a successor, and those who do back a candidate usually choose their vice-president; Joe Biden is openly considering a 2016 run.

But polls show Clinton, not Biden, is the dream candidate for many Democratic activists. If she were to run, she would be a huge favorite, and the most logical path for another Democratic candidate to upset her would be to suggest he or she, not Clinton, is the favorite of Barack Obama.

And after Sunday’s interview, in which Obama heaped praise for 30 minutes on Clinton, it will be very difficult for another Democrat to suggest Obama would not be comfortable with Hillary Clinton as president.

Follow Perry Bacon Jr. on Twitter at @PerryBaconJr.