It certainly wasn't the first time Obama, or those close to him, appeared to come down on the side of his former Secretary of State. He said of Clinton in April 2015, "She is my friend. She would make an excellent president."
He called her "wicked smart" in an interview on Politico's Off Message podcast. And in that same interview, he seemed to criticize Sanders, though not by name. He called Clinton's campaign "more prose than poetry," perhaps a subtle dig at the gap between Sanders's soaring rhetoric and relatively limited success at passing related legislation.
"I think that what Hillary presents is a recognition that translating values into governance and delivering the goods is ultimately the job of politics," Obama said, "making a real-life difference to people in their day-to-day lives." In presenting Clinton as a candidate who could actually pass legislation, Obama hinted at the biggest criticism of Sanders's candidacy: That his proposals have no chance of passing through a hostile Congress.
In a way, Clinton could probably use the Obama endorsement more. If Sanders wants "revolution" and big changes in government, Clinton's pitch to voters is essentially, "more of the same." Sanders already has support from voters who are dissatisfied, potentially leaving those who are happy with Obama's presidency to Clinton.
One thing was clearer than Obama's support for Clinton, though: His disdain for the state of the GOP primary process. The president slammed the Republican candidates, starting with – but not limited to – Donald Trump. He called anti-immigrant and anti-Muslim rhetoric "troubling." That rhetoric, combined with what he called an obstructionist GOP-held Congress, left Obama with one final thought:
“The thing I can say unequivocally here is I am not unhappy that I am not on the ballot," Obama said.