As someone who speaks regularly, I found this article interesting which looks at Barack Obamas speeches and askes what makes them successful.
They basically claim that it is a combination of evoking history and a sense that we are greater than ourselves. This is done through words and phrases that echo former great leaders. It is also down to his manner, calmness and self-assuredness when speaking. And also the range of delivery, speed, pitch and phrasing.
“His style of delivery is basically churchy, it’s religious: the way he slides down some words and hits others – the intonation, the emphasis, the pauses and the silences. He is close to singing, just as preaching is close to singing. All writing is a rhythm of kinds and he brings it out, hits the tune. It’s about the tune, not the lyrics, with Obama.” Philip Collins, former speech writer for Tony Blair, quoted in the same article.