The final state to fall into the Biden win column was Maine, which Sanders had won easily in 2016 - but the difference in 2020 was a primary was used instead of a caucus - and Biden rode that to a narrow victory.
Biden's show of strength, which stretched from New England, through the mid-Atlantic, through the Deep South, the Upper Midwest, and all the way to Arkansas, Oklahoma and Texas, was not what the Sanders campaign had expected from Super Tuesday.
Six states vote next week on March 10: Idaho, Michigan, Missouri, Mississippi, North Dakota, and Washington State.
Speaking to reporters at his campaign headquarters in his home state Vermont, Sanders showed no signs of panic, and said he welcomed a very direct comparison of his record with Biden in the months ahead.
"Joe and I have a very different voting record," Sanders said, referring to Biden's time in the U.S. Senate, which he left in 2009.
"Joe and I have a very different vision for the future of this country," Sanders added.
While the race narrowed to Biden and Sanders, Elizabeth Warren was considering her next move - Sanders said he had spoken with the Massachusetts Senator, but did not now whether she would stay in the race or not.
The next debate for the Democrats is Sunday March 15, coming just before primaries in Arizona, Illinois, Ohio, and Florida.
If Warren drops out, that debate might only involve Biden and Sanders.