While "Yankee Reconstructed" is making its way through the last hurdles of the publishing business, I thought we might use the time to fill in some historical background that will help you understand the political shenanigans going on in the story.
First, I worry a bit that with all the current political talk making the rounds, hearing the terms "Republican" and "Democrat" will lead to confusion. So please keep in mind that the political parties immediately after the Civil War bear no resemblance to their similarly-named counterparts today. What I outline below will give you a rough and dirty look at those making up the two sides.
The Republican Party (The Grand Old Party) grew out of the remnants of the Whigs around 1856 and was often referred to as "The Party of Lincoln." In the North, its members were largely white evangelical Protestants, primarily Methodists and Baptists.) They had high moralistic standards and wanted a government that would control the use of alcohol and keep people from doing business on Sundays. They were industrialists, bankers, railroad magnates, and favored high tariffs to protect their businesses. They were generally (although not passionately) in favor of getting rid of slavery, and they supported Lincoln's goal of holding the Union together because they wanted a strong country with a strong government.
In the Southern states, the party looked quite different. White Republicans tended to be Scalawags (Southerners who opposed slavery and the Confederacy) or Carpetbaggers (Northerners who came South hoping to make money from the crumbling economy.) Jonathan Grenville, in this book, was a dedicated Republican who supported abolition, emancipation, and giving Negroes full rights of citizenship.
The majority of the party, however, was made up of newly-emancipated slaves. Freed blacks made up a large majority of the population of the South, and when they worked together to achieve their political goals, they were almost invincible. Republican politicians sometimes exploited their numbers in order to gain support for themselves. For example, in South Carolina, police and fire protection was almost non-existent after the war. The Republican governor created militias by recruiting blacks who needed work. He was quick to put weapons into their hands, but less eager to actually train them in the niceties of law enforcement.
Blacks ran for both state and national offices and brought a much different attitude toward government. They were quick to realize that political power also gave them economic advantages. And from there, a slippery slope of government corruption developed --- a trait that would weaken the Republican Party.