Former Los Angeles City Controller Wendy Greuel talks to the crowd at the Ready for Hillary event Wednesday night outside The Exchange, a night club in downtown Los Angeles. (Matea Gold/The Washington Post)

The line of cars waiting to be valeted Wednesday night outside The Exchange, a night club in downtown Los Angeles, was proof of how the mechanics of politics can change in just one election cycle.

In the lead-up to the 2012 presidential election, single-candidate super PACs were still exotic new creatures, the realm of savvy political operatives and deep-pocketed donors, and largely the domain of the right. Priorities USA Action, a super PAC started in 2011 by two former White House aides to back President Obama’s election, initially struggled to get traction.

Now -- a full three years before voters select the next occupant of the White House -- a similar group is already setting the pace for the still-embryonic 2016 race.

Inside the L.A. club Wednesday night, more than 400 mostly twentysomething fans of Hillary Rodham Clinton milled around the cavernous dance floor, sipping $8 drinks such as The Rodham (Jack Daniels with peach schnapps, sweet & sour, orange juice, 7-Up and a splash of grenadine) as local politicos exhorted them to prepare for another Clinton presidential run.

Never mind that the potential candidate in question says she has not yet made up her mind.

Ready for Hillary -- a super PAC launched by Clinton fans early this year and now guided by some veteran Clinton hands -- is already whipping up excitement, disseminating bumper stickers and T-shirts and filling the vacuum left by Clinton’s silence.

“Who do we want?” shouted Michael Trujillo, a senior adviser to the group, as he stood on the stage.

“Hillary!” came the response from the crowd.

“I couldn’t be more excited,” said Sri Ramesh, a member of the College Democrats at the University of Southern California. “She resonates with me. I identify with her a lot.”

Democratic Rep. Janice Hahn sent a videotaped message calling on fans to “keep working to convince her to run” and former City Controller Wendy Greuel urged everyone in attendance to persuade 10 friends to join the effort.

“In terms of making sure we keep the presidency, it’s never too soon to start,” Greuel said in an interview. “And the support out there is kind of clearing the field, so to speak.”

The L.A. event was the fourth low-dollar fundraiser the super PAC has had around the country in recent weeks. (Entry fee: $20.16.) This one had all the hallmarks of an official campaign event: the group’s red white and blue logo projected in huge letters above the stage, a slickly produced video and pulsating pop anthems.

Being L.A., there was also the requisite surprise celebrity guest: in this case, Omarosa of “Celebrity Apprentice” fame, who reminisced about observing Hillary Clinton during her stint as a White House aide.

“I saw her fight for breast cancer awareness for women. I saw her fight for opportunities for children,” Omarosa said. “So now as we prepare to see her take the helm as the first female president of the United States, all of us have to get together and get behind this sister.”

A few minutes later, Pacific Palisades resident Katie O’Laughlin, 58, snapped a photo of her daughter Elizabeth Tauro, 24, standing in front of the Ready for Hillary logo.

“It’s never too early to get people excited and get the word out,” said O’Laughlin, whose daughter had brought her to the event.

“We’re ready to support Hillary,” Tauro said. “She has a proven track record. We know what she stands for. But not only that, but she’s a woman, and we need a woman in the White House.”

Jonathan Colmenares, 25, of West Hills, clutched a Ready for Hillary placard as he surveyed the scene. He had heard about the fundraiser on Facebook and pronounced the early activity on Clinton’s behalf “insane.”

“What are we at, three years out?” he said. “It’s sort of crazy. It’s pretty cool.”

Ready for Hillary is quickly beginning to take on the veneer of a full-fledged campaign operation. The super PAC now has 12 paid staffers working out of new headquarters in Rosslyn, Va., and a team of 30 in all, including fundraisers and consultants. The group has pocketed donations from 20,000 contributors and surpassed more than 1 million supporters on Facebook.

Next week, members of the super PAC’s national finance committee -- a group that now includes billionaire George Soros -- will meet in New York, joined by liberal activist David Brock, pollster Geoff Garin and former Michigan Gov. Jennifer Granholm.

“This isn’t a persuasion campaign,” executive director Adam Parkhomenko told the Post recently. “There are a lot of people who have already made up their minds, want her to run, and will support her if she does.”

The group’s aggressiveness has triggered some consternation in Hillaryland, as some former aides worry that the super PAC will confuse donors looking to get in early on a Clinton bid. Some of her allies have been pushing to turn Priorities USA into the main outside advertising vehicle to back her candidacy, a place to collect the really big checks that would inevitably be written to support her effort.

Ready for Hillary officials have sought to assuage concerns, capping donations at $25,000 as they stress their grassroots focus.

“I think the longer we’ve been around, people see we have her best interests at heart,” Parkhomenko said.