While Manchin's more moderate brand of politics sometimes gives Democrats heartburn, they will need Manchin to hold this seat - and a number of other Democrats to win their tight races - in order to have any chance of taking back the Senate on Tuesday.
Some political experts believe it is still possible, but it would take just about a perfect storm of results for it to happen, with Democrats holding all of their seats, and then winning a net of two GOP seats from Nevada, Arizona, Tennessee and Texas.
The President is not going back to either Nevada or Arizona, as there has been talk that another visit by Mr. Trump might not have been helpful to GOP candidates in those states.
Democrats remain encouraged by data showing early voting up dramatically in a number of states - and early voting up by younger people, who would be more likely to vote Democratic.
But Democrats need to basically draw an inside straight, leaving the Senate advantage to the GOP.
"I think we're going to do very well in the election, I must tell you," the President said to reporters on Thursday.
"I think we're doing very well in the Senate," the President added.
Now he'll get to close the deal on that in the final days of this campaign.