While his win in South Carolina will undoubtedly deliver him a boost, there is little evidence that he inspires much enthusiasm among Democrats.
To be fair, it should be noted that Paul Heideman wrote this article before last night. There is now evidence that Democrats are happy to back Biden. I have a lot of Dems in my family. Everyone had their favorite, but aside from my uncle who loves Bernie, it seems everyone is aboard the Biden train. I believe the big difference is that they like Biden as a person as well as a candidate, whereas they didn't like Hillary much as either.
Also, Bernie isn't turning out people like he did in 2016. The youth did not rock Bernie's vote. MSNBC said that Biden spent $6k in Minnesota thus far. He won it by 8%. It was a caucus then and a primary now, but Bernie beat Hillary there by 23%.
There can be little doubt that the DNC prefers Biden over Bernie. But it appears that the majority of Dem voters do too.