the Ohio Republican Party, established in 1854 to oppose the Democrats' pro-slavery schemes
https://grandoldpartisan.typepad.com/blog/2023/03/ohio-gop.html
Grand Old Partisan highlights origin of the Ohio GOP.
Early 1854, Democrats were supporting the extension of slavery into western territories. Friends of freedom reacted by organizing a Grand New Party. The process began, in Ohio, at a Columbus church on February 14th. One hundred attendees called for a convention "to utter the voice of the State for or against the extension, under the sanction of the Government of the United States, of slavery over territory now free. We earnestly invite the people to come up en masse from every county, city, village and township in the State."
March 22nd, over one thousand people gathered at the Town Street Methodist Episcopal church, which had the largest auditorium in Columbus. David Cartter, who went on to help Abraham Lincoln win the 1860 presidential nomination, said:
"I am here to act with free men to prevent an untold evil. Let us unite together in a new party, if necessary, to secure a return to the primary principles of free government. If we do not resist slavery now, all will be lost."
Ben Wade, the Senate pro Tempore during Lincoln’s administration, called on "people of all political sentiments to join shoulder to shoulder in this great cause, and show at least as much zeal and unanimity in opposing, as the South does in upholding, the spreading and extending of slavery. Let us demonstrate to the world that the people of Ohio can and will act as efficiently for right, justice and liberty as others always do for wrong, degradation and slavery."
Salmon Chase, later appointed Chief Justice by President Lincoln, declared:
"It is time to reflect, and time to act. The people must encourage their representatives, and even when they falter support and push them forward. Be true to them, and they will be more likely to be true to you. Washington is the center of the slave power, and it is often true that men who go there forget not only their principles, but too often, also, forget their God."
Following this historic gathering, a formal convention, in Columbus on July 13th, established the Ohio Republican Party.