You might want to look at the Spanish-American War. The hysteria and political motivations are obvious, and depending on how you define manipulation you can either get it for sure or at least get allegations of it.

The Red Scare. "Communism? HIDE THE CHILDREN!"

You might find a number of parallels, not so obvious, in Memoirs of Extraordinary Popular Delusions and the Madness of Crowds by Mackay.