Vice President Kamala Harris has directly attacked former President Donald Trump on immigration issues.Justin Sullivan/Getty ImagesKamala Harris in September visited the border for the first time as a 2024 presidential candidate.Harris has crafted her messaging on immigration to counter Trump's long-standing border edge.But her address in Arizona wasn't solely about winning over voters in the Southwest.Immigration is one of the defining issues of the 2024 election.So it was no surprise that Vice President Kamala Harris on Friday visited the US-Mexico border in Arizona, one of the most hotly-contested swing states in the country this year.Harris' visit to Douglas — a border city of about 16,000 people — was notable because it was her first visit to the southern border since the launch of her Democratic presidential campaign in late July.Both Harris and former President Donald Trump are fighting to win Arizona by rallying the state's suburban independents and its large Latino population.