Former Secretary of State Hillary Clinton has seen her once-formidable lead among Latino voters shrink among likely Democratic voters in the California primary, from 30 points in October to merely one point by early April.

The San Francisco Chronicle notes:

In a Field Poll released last week, Sanders had not only cut Hillary Clinton’s onetime 63-point lead in California to six points, he had also trimmed her lead among Latino voters to seven points less than two months before California’s June 7 primary. In October, Sanders trailed by 30 points. No longer are Latino voters being touted as part of Clinton’s electoral “firewall” — a term some Latinos found offensive. Far from it. Nationally, the two are in a virtual dead heat among Latinos, according to a new poll conducted by the Public Research Institute in partnership with the Atlantic magazine. “Something unusual is going on in the Latino community,” Field Poll Director Mark DiCamillo said. “You’re seeing a reappraisal of Clinton vis-a-vis Sanders. Now it is up for grabs.”

In the most recent poll, conducted by the Public Religion Research Institute in partnership with The Atlantic, Clinton is favored by 48 percent among California’s Latino voters, while Sanders is at 47 percent — a statistical “dead heat,” well within the margin of error, and a shift of 16 points since February alone, NBC News notes.

The Chronicle notes that the Sanders campaign has conducted extensive grassroots, face-to-face canvassing among Latinos. The rise of Donald Trump in the Republican primary is also a factor: Latinos have been registered to vote against Trump, but many, particularly young people, do not have a prior preference between Clinton and Sanders. Like other young voters, young Latino voters with little memory of Clinton — or socialism — often prefer Sanders.

Whatever the reason, the new polls threaten to upend the conventional wisdom about Clinton’s likely performance in many districts, particularly in Southern California, where competition will be strongest within both political parties.