Hawaii Lieutenant Governor Brian Schatz was named on Wednesday to fill the U.S. Senate seat left vacant by the death of fellow Democrat Daniel Inouye.
Schatz, 40, was appointed by Governor Neil Abercrombie, also a Democrat, to succeed Inouye for the two years remaining in the term.
Because Schatz and Inouye are from the same party, the change does not alter the balance of power in the 100-member Senate, where Democrats are expected to maintain a 55-45 majority over Republicans in January.
"I make this decision with full confidence that Brian's appointment is in the best interest of the state of Hawaii and the nation," Abercrombie said in a statement announcing the appointment.
A White House official said Schatz would fly to Washington with President Barack Obama aboard Air Force One on Wednesday night.
Schatz is expected to be sworn in Thursday, the governor's spokesman, Keith DeMello, told Reuters.
Inouye, a decorated World War Two veteran who lost an arm in battle and represented Hawaii in Congress since its statehood more than a half century ago, died last week at age 88.
The veteran senator was chairman of the powerful Senate Appropriations Committee and third in the line of presidential succession as the Senate's senior member.
Schatz became Hawaii's 11th lieutenant governor two years ago. He previously served as head one of Hawaii's largest nonprofit community social services organizations.
He also was chairman of the state Democratic Party and chaired Obama's 2008 presidential campaign in Hawaii.