In a limited company, the liability of members or subscribers of the company is limited to what they have invested or guaranteed to the company.
The current President pro tempore of the Senate is Utah Republican Orrin Hatch. Elected on January 6, 2015, he is the 90th person to serve in this office.
The Answer: For practical purposes, the president pro tempore is the highest ranking senator, as elected by the Senate. Traditionally, this is the senator who's served the longest among those in the party in power.