Your answer is The Trojan Horse.
Border ruffians contributed to the "bleeding Kansas" problem by actively terrorizing citizens of the free state. The Border ruffians came from the slave state of Missouri and in an attempt to change attitudes through force, they would actively terrorize opponents to their pro-slavery stance. The "bleeding Kansas" problem occurred as is was decided around the time of 1950 that the settlers themselves would choose whether Kansas was a free or slave state. This resulted in a flood of people from both sides rushing to settle Kansas in order to gain another state that aligned with their particular values. The period lasted until about 1959-60 and animosity persisted through the civil war.
By threatening a veto, the President can persuade legislators to alter the content of the bill to be more acceptable to the President. Congress can override a veto by passing the act by a two-thirds vote in both the House and the Senate. (Usually an act is passed with a simple majority.)
