 On April 4 , 1991 H. John Heinz III , one of the US Senators from Pennsylvania , was killed when his chartered plane collided with a helicopter inspecting its landing gear . Under the Seventeenth Amendment to the United States Constitution , the legislature of each state has the power to permit the governor to fill the vacant seat until a special election can be held . In Pennsylvania , this power had been delegated , and Governor Robert P. Casey signed a writ on May 13 , 1991 , declaring November 5 the date for a special election and temporarily appointing Harris Wofford to fill Heinz 's now @-@ vacant seat . Under Pennsylvanian law , there was no need for a primary in such a situation ; instead , both the Democrats and Republicans would each internally select their candidate , who would run in the special election . John S. Trinsey Jr . , a member of the Pennsylvanian electorate and potential candidate , challenged the <unk> of this law , claiming that it violated his rights under the Fourteenth and Seventeenth Amendments . 
