AMES, Iowa — The rise and fall of Kamala Harris over nine months this year offers a cautionary tale for Elizabeth Warren.

The California senator, 55, rose after the opening primary debates in Miami in June, but she has since hemorrhaged support and is struggling to regain her footing. She’s now at best a mid-tier candidate, with her most prominent issue, a push for Twitter to ban President Trump from the social media platform, seen as a desperate attempt for attention, even by fellow Democrats.