Lincoln was trying to appeal to Southern voters by picking Andrew Johnson as his running mate. These two men were actually very different politically speaking. Lincoln was a Republican, Andrew Johnson was a Democrat. Lincoln was from the Midwest US, Andrew Johnson was from Tennessee.
Lincoln knew that having a Democratic Vice President who once represented a Confederate state (Tennessee) would allow his presidency to appeal to a wider range of voters.
Because it had a great effect on history.
Puritan settlements in New England tended to be very strict, hard-working, and God-fearing people, who coined the phrase "Idle hands make the Devil's work"
The last one and because no one had to much power each branch was kept inline by the other.
