In 1850, most northerners would never have dreamed they would be fighting a war against the south. why did northern public opinion change?

The economic and political differences between the slave states and the free states were brewing since the Louisiana Purchase and getting worse all the time, but it was the rise of the Republican Party and the election of the Lincoln that caused Virginia to finally secede.

I hope this helps :)

a change of venue is the legal term for moving a trial to a new location. a change of venue request because venue is improper means that the removing defendant believes that the case may not be in that venue because it is improper under procedural rules.