Simplify the following text for a Grade 8 native English-speaking person.
Original: In Scotland , the Conservatives used to be known as the Unionist Party and were Scotland 's largest party during the 1950s . However in 1965 , the Scottish Unionist Party merged with the Conservative Party which triggered a decline in Conservative support across Scotland .
Simplified: and those who had founded the Scottish Party ( which later merged with the National Party of Scotland to found the Scottish National Party ) .