Simplify the following text for a Grade 6 native English-speaking person.
Original: His political career spanned over half a century , from 1917 to 1973 ; he served multiple terms as head of government and head of state , and is credited with a leading role in the authorship of the present-day Constitution of Ireland .
Simplified: Co-owner of one of the Irish Press Newspapers , he served in public office from 1917 to 1973 . Several times he was either head of state or head of government in Ireland .