Sen. Marco Rubio: "Leading us in this fight will be a man who although wounded and facing danger he stood up and raised his fist and reminded us that our people and our country are always worth fighting for." Donald Trump isn't known for easily moving past a grudge. He was so frustrated that some of his fellow Republicans dared to challenge his bid for this year's nomination that he wouldn't participate in the party's debates. But on Tuesday, Trump watched from his box inside the convention hall as as two of his most prominent primary challengers — Florida Gov. Ron DeSantis and former South Carolina Gov. Nikki Haley — urged the party to unite behind its nominee. Such moves aren't entirely unusual at a political convention, where much of the purpose is to bring together the party after a bruising primary. Bernie Sanders moved to nominate Hillary Clinton after their contentious 2016 contest. After a bitter primary, John McCain delivered a gracious speech in support of George W. Bush at the Republican convention in 2000. But the appearances by Haley and DeSantis weren't notable solely because of their overtures to Trump. They represented the type of unity that seems increasingly out of reach for Democrats, who are openly questioning whether President Joe Biden is the right person to lead them into what both parties view as a historically consequential election in November. More local videos here: https://bit.ly/2Pa0d1l Subscribe to NEXT: http://bit.ly/2eP1GwI Stay connected: 9NEWS Website: http://www.9news.com/ Facebook: https://www.facebook.com/ilike9news Twitter: https://twitter.com/9NEWS Instagram: https://www.instagram.com/9newsdenver/ Download the 9NEWS App: https://www.9news.com/appredirect/ Sign up for the 9NEWSLETTER: https://www.9news.com/email 9NEWS (KUSA) is located in Denver, Colorado.