When Donald Trump delivered his acceptance speech at the Republican National Convention, Bernie Sanders was watching.

Recently coming off his endorsement of Hillary Clinton, Sanders live-tweeted Trump’s RNC convention speech Thursday night, largely using the #RNCWithBernie hashtag.

When Trump invoked Sanders’s name as a testament to his unifying prowess, claiming Sanders supporters "will join our movement, because we will fix his biggest issue, trade deals" and that "millions of Democrats" will become Trump supporters, Sanders was there to stop him short.

Those who voted for me will not support Trump who has made bigotry and divisiveness the cornerstone of his campaign. #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

We believe in bringing people together, not dividing them up. — Bernie Sanders (@BernieSanders) July 22, 2016

Our movement understands that what we don't need is Trump's huge tax breaks for millionaires. #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

Sanders continued, fact-checking Trump on foreign policy:

Trump is wrong. The real cause of instability in the Middle East was the Bush-Cheney invasion of Iraq. By the way, where is President Bush? — Bernie Sanders (@BernieSanders) July 22, 2016

And on economic policy:

Trump’s big economic plans: Give trillions in tax breaks to millionaires, refuse to raise the federal minimum wage. #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

What a hypocrite! If Trump wants to "fix" trade he can start by making his products in the US, not low-wage countries abroad. #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

Fix trade. Stop manufacturing Trump ties in China. — Bernie Sanders (@BernieSanders) July 22, 2016

Trump’s economic plan: same old, same old trickle-down economics. Pathetic. #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

Trump’s economic plan: let states lower the federal minimum wage of $7.25 an hour, already a starvation wage. — Bernie Sanders (@BernieSanders) July 22, 2016

Sanders critiqued Trump’s character:

Trump: "I alone can fix this."

Is this guy running for president or dictator? #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

Trump: "I alone can fix this." Maybe he doesn’t understand that a president has to work with Congress. #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

And even expressed agreement with Ted Cruz:

Looks like Ted Cruz was right about one thing. Trump does not understand what the Constitution is about. #RNCwithBernie — Bernie Sanders (@BernieSanders) July 22, 2016

Trump likes say that he and Sanders are two sides of the same coin

In April, when Trump had all but locked up the presidential nomination and Clinton’s lead over Sanders was looking increasingly unbeatable, Trump began to adopt a pro-Sanders strategy.

Once having lambasted Sanders for being "beyond socialism," Trump has shifted to lamenting about the "rigged system" that prevented Sanders from challenging Clinton’s presidential bid, in a clear play for his voters.

On the surface, it's not that far-fetched an idea: "There is a distinctive anti-establishment tenor to the campaigns," Matt Dickinson, a political science professor at Middleburg College, told me in June.

It's clear that both Trump and Sanders have been able to tap into that basic economic theme. Paired with their attacks on 30 years of trade deals ruining American prosperity, Trump is trying to make a play for the frustrated Sanders supporters.

But it’s clear Sanders doesn’t agree. He said he would vote for Clinton for president, and he's encouraging his voters to follow suit.