President Donald Trump implored voters Thursday to reject Democratic Sen. Claire McCaskill and to instead install a Republican in her seat who would fully back his agenda.Trump appeared at a rollicking campaign rally in Columbia, home of the state’s largest university, in an airline hangar draped in American flags. It was his second rally in an 11-stop, eight-state tour designed to boost Republican turnout ahead of Tuesday’s crucial midterm elections. The president, accompanied by McCaskill’s Republican challenger, Josh Hawley, declared that Hawley “will be a star.”Hawley, the current attorney general, sought to link McCaskill to Trump’s Democratic opponent, Hillary Clinton, who lost the state in 2016 by nearly 19 percentage points.“Claire McCaskill has spent her lifetime in politics just like Hillary,” Hawley said. “Claire McCaskill wanted us to call Hillary Clinton ‘Madam President.’ On Nov. 6, we’re going to call Claire McCaskill ‘fired.’” Four days until midtermsWith four days to go until midterm elections that determine control of Congress, Republicans are optimistic they could make gains in the Senate, but they might struggle to maintain a majority in the House.McCaskill is among a number of vulnerable Democrats running in red states. She is a top target for Republicans seeking to expand the party’s slim 51-49 edge in the U.S. Senate.McCaskill is pitching herself as a moderate as she seeks to hold onto her seat. She has sought to distance herself from “crazy Democrats” and said in an appearance on Fox News that she supports Trump’s efforts to secure the southern border. Hawley has dismissed her efforts and argues that she is not the right fit for an increasingly conservative state.Trump said that McCaskill has been “saying nice things” but that she “wants to get elected and then she’ll always vote against us.”A check of her record, however, shows that McCaskill votes with the president about half the time, though she has opposed him on some key issues, including his tax cuts and the recent confirmation of Supreme Court Justice Brett Kavanaugh. GOP momentum blunted, Trump saysTrump expressed optimism for the midterm elections, though he noted that Republican momentum had been blunted in recent days by “two maniacs” — a reference to a mail bomb scare and a mass shooting at a Pittsburgh synagogue. He added, “We don’t care about momentum when it comes to a disgrace like just happened to our country.”However, he noted, “It did nevertheless stop a certain momentum. And now the momentum is picking up.”The president will appear twice over the next few days in Missouri, returning on the eve of Election Day to rally voters in Cape Girardeau.