Rambling Old Man Monologue: Lincoln has a habit of breaking into anecdotes that sometimes don't have any relevance to the topic at hand. Other times they're quite calculated to produce an effect.
The Unfettered: Lincoln is absolutely determined to pass the amendament, and doesn't hesitate to: use bribery to convert representatives to his side, exploit the emergency powers that the Constitution has given him, and even lie to congress about being in peace talks with the Confederacy.
Aww, Look! They Really Do Love Each Other: The night after a heated argument over whether Abe should waste his currently public approval by continuing to push his amendment, Mary tells him he better procure the remaining Democrat votes, or else he will answer to her.
Broken Bird: Mary has suffered the loss of two children, worries about her husband's safety, and fears (sadly, quite correctly) that history will remember her as a crazy woman who ruined Lincoln's happiness.
One Head Taller: The real Mary Todd Lincoln was 5'2, more than a foot shorter than her husband. Sally Field is of the same height.
The Unfavorite: Mrs. Lincoln thinks Abe sees Robert as this, while Abe suggests that Mrs. Lincoln sees Tad as this. (The film depicts their true feelings towards their sons as much more complex.)
Played By: Gulliver McGrath
Lincoln's youngest son.
Break the Cutie: When he hears his father has been shot, Tad screams in grief.
Constantly Curious: He's very curious about slavery, even examining plate images of whipped and beaten slaves. His mother worries this will traumatize him.
Innocently Insensitive: Out of childish curiosity, he asks some of the black employees of the White House, like Slade and Keckley, if they were ever slaves in the past and if they were beaten, without realizing it can be a touchy topic. Luckily they both understand.
Sleep Cute: He's introduced asleep on the floor, and his dad curls up with him.
Spoiled Sweet: Son of the President, plays with official maps, rides a goat pulled carriage through the White House, yet is a goodhearted and playful boy.
Played By: Gloria Reuben
Blue Oni: Very calm and collected in contrast with her boss and friend Mary.
The Reliable One: Of the Cabinet members, Seward is the one working closest with Lincoln during the struggle to get the amendment passed. Although even he gets frustrated coping with Lincoln's juggling act between pushing the amendment and considering meeting with the Confederate peace commission.
What the Hell, Hero?: He is not happy when he learns Lincoln arranged to meet with a Confederate Peace Commission without consulting him first.
Jerk with a Heart of Gold: Most of his conversations are peppered with insults to the whoever he's currently addressing. He's also a strong believer in racial equality who is willing to do whatever it will take to abolish slavery.
Deliberate Values Dissonance: He's portrayed as a very soft-spoken Nice Guy who openly admits to hating slavery. But he's also uneasy about abolishing it and voices opposition to giving black people and women equal rights.
Nice Guy: Very polite in general, especially in comparison to all the other democrats who staunchly oppose the amendment.
Wells A. Hutchins
Played By: Walton Goggins
Played By: David Warshofsky
Gang of Three
A trio of lobbyists hired by Seward to buy votes from the Democratic Party.
Comic Trio: Their antics throughout the film are the source of most of its humor. They have a few Greek Chorus moments during the floor debates.
Leitmotif: Almost every scene featuring these three is accompanied by a lively bluegrass piece, a marked contrast with the more somber music elsewhere in the film.
Sleazy Politician: A rare heroic example. They rely on shady backdoor deals in favor of the amendment's passage.
Vice-President of the Confederacy, leader of the peace committee.
Bigger Bad: He is this by extension to Pendleton and the anti-Amendment opposition as one of the major leaders of and representative for the Confederate government waging the Civil War (largely) to preserve slavery.
The Dragon: To the unseen Confederate President Jefferson Davis.
Token Good Teammate: Despite being a white supremacist who once declared that "Our new government is founded upon [...] the great truth that the negro is not equal to the white man", Stephens is respectful to the black Union soldiers he meets even as they're greeting him with Death Glares. The real Alexander Stephens saw the black man as inferior to the white, but did not see that as a reason to denigrate or mistreat black people. Lincoln also addresses him as "Alex", hinting to the fact that they were friends before the war.
Unflinching Walk: While his fellow Southerners pause in horror upon finding out their escort is made up of black Union soldiers, Alexander calmly keeps walking to the carriage awaiting them and politely talks to the soldiers escorting them.