LOS ANGELES (CBSLA.com/AP) — For some Bernie Sanders supporters, the “Bern” is now all too real.

Sanders, whose calls for a political revolution energized millions of voters, bestowed his long-awaited endorsement on Hillary Clinton Tuesday, the Democratic former rivals embracing and praising each other before a cheering crowd of thousands.

READ MORE: Venice Fight Results In One Dead, One Injured, One Arrested

Just two weeks shy of the Democratic National Convention, Sanders, a self-described democratic socialist, congratulated Clinton for winning the nomination and vowed to do everything he could to help her beat presumptive Republican nominee Donald Trump.

“It is no secret that Hillary Clinton and I disagree on a number of issues — that’s what this campaign has been about,” Sanders said.

The endorsement marks a sharp turnaround for the Vermont senator, who as recently as April told supporters he did not believe Clinton was qualified to be president.

“I don’t think you are qualified if you supported the Panama free trade agreement…which has allowed corporations and wealthy people all over the world to avoid paying their taxes,” Sanders said at the time.

But on Tuesday, Sanders had apparently experienced a change of heart.

READ MORE: LAPD Arrests Two Suspects Responsible For Shooting In Watts

“In these stressful times for our country, this election must be about bringing our people together, not dividing us up,” he said. “While Donald Trump is busy insulting Mexicans, Muslims, women, African Americans and veterans, Hillary Clinton understands that our diversity is one of our greatest strengths.”

The apparent flip-flop had many die-hard Bernie supporters fuming on social media.

Other Sanders supporters – including the California For Sanders campaign – defended the move as a legitimate strategy towards defeating Donald Trump in November.

Sanders was powered by an impressive online fundraising machine that raised more than $200 million and threatened Clinton’s once overwhelming lead in the Democratic primaries with the help of college students, independents and white voters drawn to his anti-establishment message. His endorsement could help bring some of those supporters into the fold for Clinton as she faces Trump.

Trump, who previously said Sanders has been “treated terribly by the Democrats” and should have run as an independent, wasted no time going after the Vermont senator.

“Bernie Sanders, who has lost most of his leverage, has totally sold out to Crooked Hillary Clinton,” Trump wrote Tuesday as part of a series of Tweets ahead of the Portsmouth event. “Sanders was not true to himself and his supporters.”

MORE NEWS: Multi-Vehicle Crash In Irwindale Closes Multiple Lanes On 605 Freeway

(TM and © Copyright 2016 CBS Local Media, a division of CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)