Former rival Chris Christie grabbed the attention of social media users who mocked his expression during Mr Trump's speech in Florida hailing the Super Tuesday results.
The New Jersey governor endorsed Mr Trump last week, after his own campaign for the Republican nomination failed.
As he stood behind his party's frontrunner, his face led some commentators to suggest he was reflecting on making a serious mistake.
Many observers likened Christie to a hostage reading a ransom note, causing #FreeChrisChristie to trend on Twitter.
Others used the lyrics to the song The Sound Of Silence by Simon & Garfunkel to mock Mr Christie's expression.
Media reports seized on the memes, with Alexandra Petri writing a homage to what she called his "wordless screaming" in the Washington Post.
"His were the eyes of a man who has gazed into the abyss, and the abyss gazed back, and then he endorsed the abyss," she said.
Whether or not Mr Christie himself believed he was in trouble on the stage in Florida, his endorsement of Mr Trump has landed him in hot water back in New Jersey.
'Utter disgrace'
Six newspapers released a joint editorial on Tuesday accusing him of neglecting his constituents and demanding he step down as governor.
They said he was out of New Jersey for all or part of 261 days in 2015, with the state paying some of the bill. They did not hold back in their criticism.
"What an embarrassment. What an utter disgrace," the editorial said.
"We're fed up with Gov Chris Christie's arrogance. We're fed up with his opportunism.
"We're fed up with his hypocrisy. We're fed up with his sarcasm."
It comes days after Hewlett-Packard chief executive Meg Whitman, a major contributor to Mr Christie's ill-fated campaign, called his endorsement of Donald Trump "an astonishing display of political opportunism".
Some commentators have suggested Mr Christie hopes to secure a top political appointment by supporting the billionaire.
Speaking on stage in Florida on Tuesday night, Mr Christie said Mr Trump had "shown himself to be tough and strong and bold".
"Tonight is the beginning of Donald Trump bringing the people of our nation together to help America win again," he said.
How much Mr Christie gains from the surprise endorsement remains to be seen.
Donald Trump was celebrating his latest victories in his bid to become US president - but for once he did not steal all of the limelight.