Robert Downey Jr., Mark Ruffalo, Joss Whedon and many other celebrities appear in a video urging Americans to vote on Election Day 2016. (Save the Day PAC)

It's generally accepted as fact that Hollywood leans left when it comes to politics. But a new political ad makes it clear: This group of celebrities does NOT like Donald Trump.

The three-minute ad, released Wednesday by director Joss Whedon's super PAC, Save the Day PAC, starts out with a familiar plea from celebrities: Register to vote, and cast a ballot on Election Day. It was the cornerstone of the "Rock the Vote" campaign that was most visible in the 1990s. P. Diddy made the same appeal in his "Vote or Die" campaign in 2004, and was subsequently mocked on Comedy Central's "South Park" for it.

But Whedon's ad takes a sharp left turn about a minute in. It swiftly transitions from pleas for voter registration to a specific appeal for the 2016 election: Don't vote for Trump.

It doesn't mention the Republican nominee by name; nor does it mention his Democratic opponent (and presumably the candidate the cast of the ad would prefer viewers vote for), Hillary Clinton.

The collective celebrities say it's tough to get a group of famous people together unless it's for a cause they really care about. That's when Don Cheadle comes in, rallying the cause against a "racist, abusive coward who could permanently damage the fabric of our society." Although the reference isn't explicit, it's clear that Trump is Cheadle's target.

It's also clear that the ad is meant to appeal to young voters who might not otherwise be excited about the election. The dreamlike music underneath the scripted lines is intended to give viewers a sense of hope and wonder, to convey that these celebrities are involved with something special and transformative. The ad's cast hits a couple of Democratic go-tos – "common-sense gun laws" is a favorite of President Obama's.

It's the kind of appeal to young voters that will be crucial in the last six weeks of this election campaign. Although Clinton leads Trump among young voters by a wide margin — more than 20 percentage points, according to recent Quinnipiac polls — in a four-way race with Trump, Libertarian nominee Gary Johnson and Green Party nominee Jill Stein, Clinton leads Johnson by only 5 percentage points.

“You want something to vote for, not just against,” Clinton told young voters at a millennial-targeted rally in Philadelphia on Monday. Well, this ad doesn't exactly give that to viewers. But it does show that liberals know they have work to do with young voters and that they see them as a critical voting bloc in November.