WASHINGTON - Sen. Patrick J. Leahy (D., Vt.) formally assumed a position in the presidential line of succession Tuesday, becoming the Senate Pro Tempore after the death of Sen. Daniel Inouye (D., Hawaii).

Vice President Biden administered the oath of office to Leahy from the Senate rostrum, with Sen. Bernard Sanders (I., Vt.) and Senate Majority Leader Harry Reid (D., Nev.) standing behind him.

At least 28 senators, seated at their desks, were present for the ceremony and stood to applaud once Leahy took the oath. Leahy shook the hands of Sens. Jon Kyl (R., Ariz.) and Orrin G. Hatch (R., Utah), as he returned to his seat.

Per tradition, the Senate opened Tuesday morning with a black drape and a dozen white roses placed over Inouye's desk, which is located behind Reid's desk and podium and next to desks occupied by Sen. John Kerry (D., Mass.) and Leahy.

"I can't tell you how much it pains me. He was one of the greatest members of this body ever to have served, and a dear friend to so many of us," Leahy said before taking the oath. "He's perhaps the best role model for public service any American could ask for."

"Senator Inouye's story is one of great passion for his people," Leahy said, pausing to hold back tears, before adding, "Commitment to his calling in public service and dedication to finding a better way forward for all Americans. A true patriot."

Leahy, 72, was first elected to the Senate in 1974. Born in Montpelier, Vt., he grew up near the Vermont state capitol and was a lawyer before winning his Senate seat.

Leahy currently chairs the Senate Judiciary Committee, but is now also in line to succeed Inouye as chairman of the powerful Senate Appropriations Committee.

Inouye was the second-longest serving senator in U.S. history, behind Sen. Robert Byrd (D., W.Va.), who died in 2010. He was first elected to the House in 1959 - the year Hawaii became a state - and won his Senate seat in 1962.

As Sen. Daniel Akaka (D., Hawaii) noted Monday evening in an emotional tribute to his colleague, Tuesday was the first day in the history of Hawaii that Inouye did not represent the state in Congress.