Vice President Joe Biden, right, administers the Senate oath to Sen. Paul G.
AP – Vice President Joe Biden, right, administers the Senate oath to Sen. Paul G. Kirk Jr., D-Mass., left, …

WASHINGTON – Former Democratic Party chairman Paul G. Kirk Jr. stepped in Friday as the temporary replacement in the Senate for his longtime friend, the late Edward Kennedy.

Kirk said taking over the Massachusetts seat left him with mixed emotions, particularly because he was still feeling the "profound absence" of his old pal.

"It's exhilarating and sobering at the same time," Kirk said.

Democrats applauded his arrival. Kirk's swearing in by Vice President Joe Biden gave Senate Democrats a filibuster-resistant, 60-vote majority with the health care fight at a critical juncture. Contentious battles also lay ahead on climate change and financial regulation.

The swearing in came just a few hours after a Massachusetts judge rejected a Republican request to delay it.

The state GOP had argued that Democratic Gov. Deval Patrick exceeded his constitutional authority by appointing Kirk before a traditional 90-day legislative waiting period had expired. State lawmakers passed a bill this week giving Patrick the power to choose an interim senator. - Also known as "making up the rules as you go along".

Kirk said he did not spend much time worrying about the GOP's legal challenge.

"We're prepared to go to work," he said.