What was the name of the new political party, formed to block the spread of slavery, that abraham lincoln joined?

The republican party. (a p e x)

A pocket veto is a bill that still becomes law despite the act of a veto on behalf of the president. The reason that the bill becomes a law is that the president does not veto the bill within ten days. Once the ten days have lapsed, the bill will become a law regardless of whether the president vetoes the bill after.