A 2018 study found negative views of immigrants strongly predicted support for Trump in the 2016 GOP primaries. Attitudes toward immigration were a more potent factor for Trump than for prior GOP candidates McCain and Romney. Trump's popularity has increased among Republicans who support the deportation of undocumented immigrants, with the percentage favoring this position rising from 41% in the 2016 New Hampshire primary to 55% in 2024. Immigration was the top issue for 30% of New Hampshire GOP voters in 2024, up from 15% in 2016.