What was the message of the political cartoon "The 'Rail Splitter' At Work Repairing the Union"?
O Lincoln was bringing the Union back together, but his vice president, Andrew Johnson, was
undermining him.
Lincoln wanted to bring all the freedmen into the Union as full citizens, but Southern Democrats
were blocking this goal.
Lincoln and his vice president, Andrew Johnson, were being too lenient with the South, trying to
"stitch" the country back together and pretend nothing had happened.
Lincoln was trying to bring the Union back together, but Congressional infighting and political
squabbling was making it impossible.

Lincoln and his vice president, Andrew Johnson, were being too lenient with the South, trying to  "stitch" the country back together and pretend nothing had happened.

Explanation:

After the Union won the civil war, a new problem occurred. The federal officials debated whether they should punish the southern confederates or not.

Lincoln and Johnson wanted the north and southern states to Unite again, So, he believed the southern states should not be punished too harshly. This made a lot of people angry.

The cartoon was made to criticize Lincoln's leniency. Many people believed that Lincoln was the one that play the biggest role in dividing the country and they want Lincoln to be strict with his conviction and punish the Sothern states.