Taking a cue from Donald Trump's playbook, former Democratic presidential candidate Martin O'Malley unveiled a nickname poking fun at the presumptive GOP nominee Friday night.

"Donald Trump, he likes to hand out those little nicknames. I've got one for him: Chicken Donald," the former governor of Maryland said at the Democratic state convention in Sioux Falls, S.D. Trump has made it a campaign mainstay to knock down his political opponents with nicknames, including "Crooked Hillary" to mock presumptive Democratic candidate Hillary Clinton and the scandals that have haunted her campaign.

"Like most bullies, Chicken Donald walks away when things get tough, and real people get hurt," O'Malley added, according to tweets from his official Twitter account.

O'Malley ended his campaign in February after a poor showing in the Iowa caucuses and is now urging his fellow Democrats to unite behind presumptive nominee Clinton.

"Unlike that fascist, carnival-barker, Donald Trump — Hillary Clinton will not back down from a tough fight," O'Malley said.

He addressed district delegates in South Dakota on Friday along with President Obama's Agriculture Secretary Tom Vilsack.