Shallow celebrity cons media and vows "America First" on way to winning the presidency
The book is "The Plot Against America" by Phillip Roth and was written in 2004.
The only difference is that it is an alternate history where the celebrity was American hero Charles Lindbergh and he was named the Republican nominee for president in 1940 vs FDR. Lindbergh, using the slogan "America First" and vowing to stay out of the war in Europe barnstormed the country in his airplane to fly from campaign stop to campaign stop. FDR and the Democrats wrote him off as a shallow, anti-Semitic and naive celebrity who engaged in publicity stunts, but the media loved him and the crowds ate up flying from stop to stop.
The book is told from the perspective of young Phillip Roth (age 9 in 1940) growing up in a Jewish ghetto in Newark, NJ
I won't give away too much, but it's an interesting book and definitely a parallel to Trump in 2016.
In a bit of irony, i'm listening to the audiobook version and it's narrated by Ron Silver, the actor who became a RW Bush supporter after 9/11. The author of the book (Roth) is obviously very liberal and loves FDR.