Stump Speech

A “stump speech” originally was a speech (often given by a political candidate) where the speaker stands on a tree stump. The term “stump speech” has been cited in print since at least 1810.
 
“Stump speech” has endured as a term to describe a speech given on any raised platform (not necessarily a tree stump).
   
 
Wikipedia: Stump speech (politics)
A political stump speech is a standard speech used by a politician running for office. The term derives from the custom in 19th century America for political candidates campaigning from town to town to stand upon a sawed off tree stump to deliver a standard speech. Because the busy pace of campaigning often forces candidates to address people several times per week or even per day, the candidate and his or her staff will usually write a single speech to be delivered at most public appearances. The beginning of the speech is usually tweaked to include mentions of local elected officials and campaign staff, with local references sometimes peppered throughout, but most of the speech remains identical from day to day.

(Oxford English Dictionary)
stump speech n.
1820 J. Flint Lett. from Amer. (1822) 251   The harangues are called stump-speeches.
1839 Proffit in Congr. Globe 31 Dec. 72/2   He could make‥a better stump speech himself.
 
1 August 1810, Georgia Journal (Milledgeville, GA), pg.1, col. 2:
And I would urge him, should he again attempt stump speeches, to avoid addressing the people as “gentlemen of the jury” to shew himself a Lawyer, and assure him that the “merits of his case,” if not otherwise stated, will before the election be laid beforethe public, by a citizen of
BALDWIN.
 
22 October 1812, Greensburgh and Indiana Register(Greensburgh, PA), pg. 3:
Stump speeches.
 
Google Books
Letters from America:
Containing observations on the climate and agriculture of the western states, the manners of the people, the prospects of emigrants, &c
By James Flint
Edinburgh: W. & C. Tait
1822
Pg. 251:
Jeffersonville, (Indiana,) Sept. 8, 1820.
(...)
The number of cases of litigation before the various courts of justice is very great; and there are numerous opportunities for exerting popular talent, as at elections, where the harangues are called stump-speeches, from the practice of candidates moutning the stumps of trees, and there addressing themselves to the people, and in State Assemblies.
 
Google Books
Memoir of the life of Josiah Quincy Jun. of Massachusetts, by his son, Josiah Quincy
By Josiah Quincy
Boston. MA: Cummings, Hilliard
1825
Pg. 5:
Traditions have come down to (Pg. 6—ed.) us of his sprightliness as a school-boy, and one old neighbor told the brother of Prentiss—after his fame as an orator began to spread — that he had heard the first stump-speech of the wonderful youth in an apple-orchard hard by to a mass-meeting of his playmates.

7 October 1825, Richmond (VA) Enquirer, pg. 3:
Was he in danger,when in a stump speech, he declared the efforts to amend the constitution treason” in the presence of a large “assemblage unknown to the laws of the land,” a great majority of whom were opposed to him in sentiments, and voted for a Convention?
 
Google Books
13 May 1826, Niles’ Weekly Register, pg. 192, col. 2:
... which they could not do, the argument of his friend to the right; or under color of a message to the house to announce an electioneering arrangement, what, in Maryland, was known by the name and appellation of a stump speech.