Richard Spencer, the alt-right leader and white nationalist who fervently backed President Donald Trump's 2016 election campaign, said he's off the Trump Train after the president greenlighted an attack on Syria Thursday night.

But Spencer already hopped aboard a new political bandwagon: that of Rep. Tulsi Gabbard, a Democrat from Hawaii who has taken a strong anti-interventionist stance.

"Tulsi Gabbard 2020 #Trumped," Spencer tweeted late Thursday night, after Trump's Syria strike was carried out.

Gabbard is an unorthodox politician.

She strongly backed Sen. Bernie Sanders' Democratic presidential primary bid — but her rhetoric often sounds more like Trump's than Sanders'.

Gabbard backed a Republican-sponsored bill in 2015 that would have increased vetting for refugees from Iraq and Syria in the wake of a terrorist attack in Paris in November 2016.

And she's strongly against American intervention in the Middle East, just as Trump said he was during the campaign.

Gabbard even met with Syrian President Bashar Assad in January — and came back from the experience saying Assad should remain in power, despite the fact that he's been murdering his own people for years.

"Whatever you think about President Assad, the fact is, he is the president of Syria," Gabbard told CNN. "In order for any possible viable peace agreement to occur, there has to be a conversation with him. The Syrian people will determine his outcome and what happens with their government and their future."

Tulsi Gabbard at the 2016 Democratic National Convention J. Scott Applewhite/AP

Like many of Trump's strongest backers, Gabbard is outraged that Trump tossed aside his campaign rhetoric and launched an attack on Syria Thursday night.

"It angers and saddens me that President Trump has taken the advice of war hawks and escalated our illegal regime change war to overthrow the Syrian government," Gabbard said in a statement. "This escalation is short-sighted and will lead to more dead civilians, more refugees, the strengthening of al-Qaeda and other terrorists and a direct confrontation between the United States and Russia — which could lead to nuclear war."

It's unclear how serious Spencer is about his support for Gabbard.

However, it's clear he's angry that Trump changed his policy on foreign intervention, despite promising an "America First" agenda — despite the nationalist agenda reportedly pushed by White House chief strategist Steve Bannon.

"If Bannon does not resign, I will have lost a tremendous amount of respect for him," Spencer tweeted. "#NoWarInSyria."