2020 Dem Primary: President Hillary Clinton vs Rep. Tulsi Gabbard

[Shaula🏳️‍⚧️]

In a timeline where Hillary wins 2016, Gabbard stays in progressive's good graces (viewed like she was ITTL in August 2019 for example) because there's no Trump impeachment for her to vote "present" on and attacking Democrats is viewed more as being from the left now (because Democrats are the ones in office).
Clinton send more troops to Syria, gets involved in a War in Iran and fails to get any major policy breakthroughs done mostly because of the GOP congress which has a massive majority due to the 2018 midterms which are worse than 2010. She is broadly unpopular and her trade, domestic and foreign policy actions cause her to be hated by many democrats too.
Despite this no major democrat challenges her (Bernie floated the idea but decided against it).
Tulsi Gabbard (who hates Hillary) decides in May 2019 to primary the unpopular President Clinton from the left, mostly attacking her for being a "warmonger", for her affinity for free trade and for her failures to get anything done relating to healthcare. While most democrats and the entire establishment backs Clinton, Bernie Sanders and the Squad (which is larger than the ITTL Squad because of energy on the left being more directed at centrist Democrats than Republicans) endorsing Gabbard.
Gabbard almost certainly won't win, but how well would she do in this situation?

[Blow by blow, the passion dies]

Gabbard might pull surprise wins in Iowa and likely New Hampshire, but the DNC likely wouldn't want her to be nominated. Given Tulsi's relatively conservative stances on social issues in the past, Democrats would attack her as a flip-flopper. On Super Tuesday, Tulsi would carry American Samoa, Minnesota, Utah, Massachusetts, Vermont and Maine, with Hillary Clinton eating the rest (narrowly winning California) and keeping New England competitive.

Gabbard would drop out after losing Ohio by 44-55.

[Vice President Christian Man]

As much as I love Tulsi, I doubt she'd successfully primary Clinton. I'm guessing she'd get about 7-8% of the primary P.V.

[Chillary]

Depends entirely on how Tulsi runs her campaign. If she runs like a Bernie type progressive, she could win a few states like Vermont, Oregon, and Hawaii.

Overall though, she would have zero chance at actually winning the nomination.