JD Vance, previously a vocal critic of Donald Trump, is set to debut as Trump's running mate at the Republican National Convention. His keynote speech marks a dramatic shift from criticism to staunch advocacy for Trump's political movement, positioning him as a potential leader reshaping the GOP. At 39, Vance's candidacy as the first millennial on a major party ticket raises significant questions about the age of top contenders like Trump and President Joe Biden, both in their late 70s and early 80s.

Vance's personal narrative, from a challenging upbringing in Kentucky and Ohio to becoming a Marine, Ivy League graduate, successful businessman, and bestselling author of "Hillbilly Elegy," will likely feature prominently in his address. Initially critical of Trump, whom he once compared to "America’s Hitler," Vance's views evolved during his 2022 Senate run in Ohio, culminating in Trump's endorsement pivotal to winning the party nomination.

As a fierce defender of Trump since then, Vance has campaigned vigorously alongside him and embraced Trump's policies, including the controversial "America First" foreign policy. Despite criticisms, Republicans plan to highlight themes of American global strength under Trump's presidency, contrasting it with what they see as diminished U.S. standing under Biden's leadership. However, their stance on issues like U.S. support for Ukraine amid Russia's invasion remains a point of contention and criticism from Democrats.