Henry Clay: The Essential American, David S. and Jeanne T. Heidler point out that Jacksonian accusation that there was a “corrupt bargain” between Henry Clay and John Quincy Adams arose even before Adams was elected president.
The House vote among the three finalists for the presidency in 1824 (Andrew Jackson, John Quincy Adams and William H. Crawford) was scheduled to be held on February 9, 1825.
One month earlier, on the evening of January 9, 1825, Clay had met privately with Adams in the latter's study for about three hours. “Most of what was said there would remain forever behind the room's doors, for neither man left a lengthy account of their discussion.”
In the following weeks, Clay began lining up votes for Adams. On January 24, 1825, irate Jacksonians learned that the Kentucky delegation in the House would cast its vote for Adams, defying instructions from the state legislature to vote for Jackson.
The Jacksonian assault began the next day, some two weeks before the House voted. The opening volley took the form of an anonymous letter that appeared in the January 25, 1825 edition of the Philadelphia Columbian Observer. A Pennsylvania Congressman by the name of George Kremer later claimed that he wrote the letter, although there is apparently substantial doubt as to his authorship.
I searched around the internet and found a copy of the letter here. It reads as follows (some paragraph breaks added):
I take up my pen to inform you of one of the most disgraceful transactions that ever covered with infamy the Republican ranks. Would you believe that men professing Democracy could be found base enough to lay the axe at the very root of the tree of Liberty? Yet, strange as it is, it is not less true. To give you a full history of the transaction would far exceed the limits of a letter. I shall, therefore, at once proceed to give you a brief account of such a bargain as can only be equalled by the famous Burr Conspiracy of 1801.
For some time past, the friends of Clay have hinted that they, like the Swiss, would fight for those who would pay best. Overtures were said to have been made by the friends of Adams to the friends of Clay, offering him the appointment of Secretary of State for his aid to elect Adams. And the friends of Clay gave this information to the friends of Jackson, and hinted that if the friends of Jackson would offer the same price, they would close with them. But none of the friends of Jackson would descend to such mean barter and sale. It was not believed by any of the friends of Jackson that this contract would be ratified by the members from the States who had voted for Mr. Clay.
I was of opinion, when I first heard of this transaction, that men, professing any honorable principles, could not, nor would not, be transferred like the planter does his negroes, or the farmer his team and horses. No alarm was excited - we believed the Republic was safe. The nation, having delivered Jackson into the hands of Congress, backed by a large majority of their votes, there was on my mind no doubt that Congress would respond to the will of the nation, by electing the individual they had declared to be their choice.
Contrary to this expectation, it is now ascertained to a certainty that Henry Clay has transferred his interest to John Quincy Adams. As a consideration for this abandonment of duty to his constituents, it is said and believed, should this unholy coalition prevail, Clay is to be appointed Secretary of State. I have no fears on my mind - I am clearly of opinion we shall defeat every combination. The force of public opinion must prevail, or there is an end of liberty.