That's not unique, they belong to the same party.
What is different is he doesn't seem to grasp the line.
He can sing her praises, he can urge people to vote for her.
But as a sitting president not running for re-election, he's not supposed to engage in attacks.
He's coming dangerously close to abuse of office with his remarks about the Republican presidential candidate Donald Trump.
Maybe he thinks all bets are off after Supreme Court Justice Ruth Bader Ginsburg interjected herself into the election?
(She has since rightly noted she should have kept those thoughts to herself.)
But he's on the line if he hasn't already crossed it.
He may not be aware of what he's doing.
It might be part of his long standing habit of making everything about him.
That annoying feature's been noted repeatedly during his two terms as president. For example, from 2012, Emily Yoffe's "Today We Are Gathered … To Hear More About Me" (SLATE).
He needs to realize he is a sitting president and start conducting himself in that manner.
His thoughts on the Republican candidate are not needed.
This is an election and he can fully support Hillary Clinton without slamming or even referring to Donald Trump.