Former UN Ambassador Nikki Haley and Florida Gov. Ron DeSantis delivered some of their sharpest attacks yet on former President Trump during back-to-back town halls Thursday — trying to dent the GOP front-runner's lead less than two weeks before the Iowa caucuses.

The big picture: Haley warned "chaos follows" Trump during her segment of the CNN town halls in Des Moines, Iowa, while DeSantis targeted Trump's stands on key issues such as abortion and immigration.

Zoom in: Haley, who has had a surge of momentum in recent weeks, said that Trump was "the right president at the right time" when he was first elected in 2016.

• "But the reality is, rightly or wrongly, chaos follows him and we all know that's true," Haley said.
• "We can't have a country in disarray and a world on fire and go through four more years of chaos," she added. "We won't survive it."

Meanwhile, DeSantis said during his town hall that Trump has "flip-flopped" on abortion and criticized the former president as "not pro-life" — even though Trump often touts having appointed three conservative Supreme Court justices who helped overturn abortion rights under Roe v. Wade.

• DeSantis, who for much of his campaign has avoided criticizing Trump directly, on Thursday took a jab at the legal peril faced by the former president, who has been charged with 91 felony counts in four indictments.
• "We're putting the future of the Republican Party and the future of the nation, perhaps, in the hands of 12 jurors," DeSantis said, in reference to Trump's federal 2020 election subversion case.

Of note: Haley on Thursday responded to a question about a New Hampshire town hall last week that sparked criticism when she did not mention slavery when talking about the reason for the U.S. Civil War.

• "I should have said slavery right off the bat. But if you grow up in South Carolina, literally in second and third grade, you learn about slavery," Haley said.
• "I had Black friends growing up. It is a very talked-about thing," she added.
• "I should have said slavery. But in my mind, that's a given, that everybody associates the Civil War with slavery."

What to watch: The two Republican presidential hopefuls, who are battling to secure the spot as the top Trump alternative, are both set take the same stage next week during the final debate before the Jan. 15 Iowa caucuses.

Go deeper: Biden focuses on Jan. 6 to cast Trump as a threat to the U.S.