Actor Susan Sarandon speaks at a rally outside the US District Court in solidarity with the Standing Rock Sioux Tribe in their lawsuit against the Army Corps of Engineers, in Washington, DC, on 24 August. Riccardo Savi SIPA

Susan Sarandon has just endorsed the Green Party’s Jill Stein in next Tuesday’s US presidential election.

The Academy Award-winning actor previously backed Bernie Sanders, who lost the Democratic primary race to Hillary Clinton.

But rather than fall into line behind the Democratic nominee, Sarandon has made clear why she won’t vote for Clinton.

In a Facebook post announcing her endorsement of Stein, Sarandon lists her disagreements with Clinton over the minimum wage, opposition to legalizing marijuana, and her support for fracking and offshore drilling.

Sarandon is also backing the Standing Rock Sioux in their struggle to stop an oil pipeline being laid across their tribal land in North Dakota.

“Fear of Donald Trump is not enough for me to support Clinton, with her record of corruption,” Sarandon writes. “Now that Trump is self-destructing, I feel even those in swing states have the opportunity to vote their conscience.”

Sarandon is not the first celebrity to advocate for radical change on these and other issues.

But the Hollywood star lists one objection to Clinton that does stand out: “She supports unconditional military aid to Israel.”

Even in 2016, it is still unusual for major Hollywood stars, even those who are vocal about left-wing politics, to take on Israel.

Perhaps this is another sign that one of the big taboos in American politics is being shattered.