(Updates with conference starts, speaker quotes)
WASHINGTON, March 14 (Reuters) - Two U.S. senators seen as possible candidates for the 2016 presidential election brandished their conservative credentials on Thursday as Republicans sought to regroup after their bruising election loss last year.
Senator Marco Rubio of Florida touched on keystone issues for social conservatives in his speech to the Conservative Political Action Conference, or CPAC. He spoke against same-sex marriage and abortion and jokingly described liberals are "freeloaders."
Rubio's Hispanic background - he is the son of Cuban immigrants - has raised his profile in a party looking to win over Latino voters after they overwhelmingly picked President Barack Obama over Republican Mitt Romney in November's election.
While Rubio has taken a leading role in negotiations over immigration reform in the Senate, he did not mention the topic in his 20-minute address.
Organized by the American Conservative Union, the annual CPAC meeting is a traditional showcase for the party's election hopefuls.
Senator Rand Paul of Kentucky said the Republican Party needed a shake-up and should emphasize libertarian values.
"The GOP of old has grown stale and moss-covered. I don't think we need to name any names, do we? Our party is encumbered by an inconsistent approach to freedom. The new GOP will need to embrace liberty in the economic and the personal sphere," said Paul, the son of 2012 presidential candidate Ron Paul.
Paul won admirers by talking on the Senate floor for almost 13 hours nonstop last week in a procedure known as a filibuster, using the confirmation process for Obama's new CIA director to raise questions about the administration's ground rules for using drones in the United States.
Some senior Republicans are noticeable by their absence from this year's conference.
New Jersey's Chris Christie, a Republican governor in a Democratic-dominated state, holds one of the highest approval ratings in the country but was not invited.
Christie upset some Republicans by praising Obama's handling of the disastrous effects of Superstorm Sandy, which slammed New York and New Jersey just days before the election.
Virginia Governor Bob McDonnell went to the conference the last two years, but will not attend this year. He ruffled Republicans' feathers by signing a transportation bill that included a tax hike.
On Friday, Romney will address the meeting, making his first major public speech since the election. (Reporting by Samuel P. Jacobs; Editing by Frances Kerry and Vicki Allen)
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