Another example, more recent, is Churchill's speech to the House of Commons on June 4, 1940, particularly the final paragraph though his rhythm and repetition occurs throughout the speech to a lesser degree. Again a fine example of free verse.
Churchill's speech served multiple purposes. Firstly it needed to inspire the British people to continue the war. Secondly it needed to send a firm message to Hitler and Roosevelt that Britain was continuing the fight even without France. Thirdly it was part of a campaign by Churchill to obtain 50 moth-balled destroyers from the US that were needed for convoy escort. To that end it was vial that the US believe that Britain would continue the fight to the bitter end, and that the us would not be releasing the vessels only to have them attacking US commerce soon after. It would appear that the speech achieved all three objectives admirably.
Looking further back, one is left to wonder if all of Henry V's St. Crispins' Day address to his troops was wholly Shakespeare, or if any was possibly original Henry.
Update from Wikipedia on Prose:
On this point [distinction of prose from poetry] Samuel Taylor Coleridge requested, jokingly, that
novice poets should know the "definitions of prose and poetry; that
prose,—words in their best order;
poetry,—the best words in their
I just remembered MLK's I Have a Dream speech, particularly the second half. This speech was a seminal moment in the Civil Rights movement of the 1960's. An estimated one million attendees, white as well as black, attended in the Washington summer heat expecting the performance of a lifetime from King, and he delivered. I find it easy to imagine that any unsatisfactory performance by King on this occasion might have set the civil rights movement back, by disheartening the grass-roots support that it so depended on. Instead, King delivered probably his finest speech, to his largest audience.