While the boss is away, the vice president will play.Vance has also become the face of Trump's Iran peace deal. The ambitious 41-year-old Vance has played a key role in negotiations with Iran, but that comes with big risks. (via REUTERS)JD Vance has been all over the US airwaves promoting his new book about his Christian faith this week while President Donald Trump has been at the G7 in France.Also Read| Donald Trump signs the US-Iran peace deal MoU during dinner with Macron in France"Let's talk about the book, I'm here to sell books!" Republican Vance joked as he made a rare foray onto "The View," a liberal-leaning daytime talk show on the ABC network.But Vance is selling more than just books -- he's also become the face of Trump's Iran peace deal.In interview after interview, Vance has repeatedly defended the fragile agreement, despite the fact that the former US marine was reportedly against the conflict in the first place.The ambitious 41-year-old Vance has played a key role in negotiations with Iran, but that comes with big risks.Trump himself has joked about blaming his "veep" if the deal fails."If it works out, I'm going to take the credit. If it doesn't work out, I'm blaming JD," Trump said in his closing G7 press conference.- 'Arrogant desire' -The political stakes for Vance may be even greater, given that he is widely assumed to be eyeing a run for US president in 2028, and both the book and a successful Iran deal could play a key role in that.No self-respecting US presidential candidate enters the race without a memoir, and Vance's new book is his second published work, following his bestselling "Hillbilly Elegy" in 2016."Communion: Finding My Way Back to Faith" is far more reflective, and appears to be a deliberate attempt to set himself apart from Trump.The book recounts Vance's conversion to Catholicism, a long road from the vaguely defined Christianity of his beloved, gunpacking grandmother who cared for him for most of his childhood.Vance speaks of an "arrogant desire to rise above others" sparked by being a "poor kid" who was "desperate to make it.""Well, now I have. I am the Vice President of the United States, among the youngest in history to hold the office," he writes. But he adds: "I had lost something important that had, for all my outward advantages, enriched me as a kid."The man once dubbed Trump's attack dog takes a softer tone in the book than he does on social media, devoting much of it to praising his Hindu-raised wife Usha, with whom he is expecting a fourth child this summer.Meanwhile, Vance is also a convert to Trumpism."Hillbilly Elegy" depicts a hollowed-out, opioid-hooked US rust belt, and its accounts have been called prophetic of Trump's rise when it was published in 2016.Yet that same year Vance compared Trump to Hitler.The vice president insists in "Communion" that his subsequent shift to becoming a Trump true believer was not a "cynical maneuver."- 'Next apprentice' -But the unspoken message behind Vance's positioning of himself as a Christian moralist is that brash billionaire Trump, with his long tail of scandals, is anything but that.Vance has been coy on whether he will run to succeed Trump in 2028."Does it really sound like the president of the United States to run a televised program for who would be his next apprentice?" Vance told Fox News -- a joking nod to Trump, who once hosted the reality TV competition show "The Apprentice."But a sign of Vance's thinking is that he also said this week that he would make a decision after the crucial US midterm elections in November.If Republicans lose control of Congress -- as many in the party fear -- Vance will have little choice but to start to distance himself from a lame-duck Trump.Yet Trump may still have the last word on what is shaping up to be a battle between Vance and Secretary of State Marco Rubio to inherit the MAGA mantle.During a dinner with Rupert Murdoch last year, Trump asked the media baron -- in front of Vance and Rubio -- which of them he preferred, according to the upcoming book "Regime Change" by two New York Times journalists.Murdoch replied that Vance had the "potential to be great" -- while Rubio was “brilliant.”