Republican presidential candidates Ron DeSantis and Nikki Haley squared off in a tense debate on Wednesday, trading barbs just days before the Iowa caucuses. Donald Trump, the consistent frontrunner in the race for the party's 2024 nomination, once again chose not to attend and held a Fox News town hall event at the same time. But despite the former president's commanding lead in the polls and absence from the stage, the stakes were still high at the debate in a snowy Des Moines. DeSantis and Ms Haley are battling to position themselves as the main alternative to Trump in the race, and both will be hoping a strong second place finish in Iowa on Monday could breathe new life into their campaigns. Here's what we learned when they went head to head. Things got off to a heated start when the pair traded insults in their very first answers. DeSantis, 45, began proceedings by calling his opponent "another mealy-mouthed politician that tells you what she thinks you want to hear". Ms Haley then shot back and took aim at what she called DeSantis's repeated "lies". "You're going to find out about a lot of Ron's lies," she said. There have been four Republican debates before this, but the one-on-one nature of this one, which was hosted by CNN at Drake University, resulted in far more direct attacks and testy exchanges. It seemed as though both were hoping to land a knockout blow before Republicans in Iowa kickstart the next phase of this race and pick their preferred presidential candidate on Monday. The theme of the night? Attack, attack attack. As the two candidates battled on stage, the former president was three miles (5km) away holding an event with his supporters. The question of his absence, and his lead in the polls, unsurprisingly came soon in the debate. DeSantis accused the former president of "running to pursue his issues" and ignoring the needs of American families. He said Trump spewed "word vomit" on social media and cast doubt on his ability to get through the legal battles he is facing. Ms Haley, for her part, once again said that she did not believe "Trump was "the right president to go forward". Both were more vocal in their criticism of him than in previous debates, taking aim at his handling of issues ranging from the pandemic to border security and relations with China. Border security and immigration came up repeatedly, a reflection of the polls that show it is a primary concern for Republican voters in Iowa and around the US. DeSantis urged the crowd to "not trust" Ms Haley with immigration. "That's like having the fox guard the henhouse," he said, pointing to earlier comments in which she referred to the term "illegal aliens" as "disrespectful". Ms Haley mostly struck a more nuanced tone on the subject, referring to the root causes of migration in Central and South America and touting her credentials as a former ambassador to the United Nations. She did, however, say undocumented migrants should be deported for "cutting the line". The war in Ukraine proved to be one of the most contentious issues of the night, and both candidates sparred with one another over their positions on the conflict. Ms Haley hit out at DeSantis for initially backing US funds for Ukraine, and then later changing his position. "Nobody knows what he believes," she said. "Let me tell you why Ukraine should matter. This is a freedom loving country," she said, adding that it was a "friend" of America. DeSantis responded by saying the war needed to end, and "people like Nikki Haley care more about Ukraine's border than our southern border". The audience of 200 or so at the venue in Des Moines were far from raucous, but DeSantis seemed to get the larger share of the applause. Some of his comments, including one moment where he described Ms Haley as having a problem with "ballistic podiatry" (in other words, shooting herself in the foot) prompted a good response in the room. That is perhaps unsurprising, as Iowa is widely seen as more favourable to him than other states such as New Hampshire, where the second Republican contest will take place and Nikki Haley is expected to perform better. Ms Haley did have some memorable moments herself, and received a loud cheer when she described the Capitol riot on 6 January 2021 as a "terrible day". But in a room not far from the venue, at his separate town hall, Trump experienced a stronger reaction. His supporters shouted "we love you" throughout the event and he shook hands for more than ten minutes after it finished. Ultimately, if DeSantis and Ms Haley are to seriously challenge the former president, they will need to tempt some Iowan voters away from him before Monday's critical caucuses. — BBC