WASHINGTON -- Three chief contenders for the Republican presidential nomination made their case as the most conservative candidate Friday, wooing the party's activist core at the Conservative Political Action Conference.

Newt Gingrich, Mitt Romney and Rick Santorum all have been CPAC regulars in recent years, but each faced uncommon scrutiny amid the escalating presidential race. Their speeches packed thousands of spectators into a large auditorium, and young volunteers hawked their stickers and signs in crowded hallways. The fourth remaining candidate, U.S. Rep. Ron Paul of Texas, chose not to attend CPAC this year.

Gingrich, as he often does, sought to connect himself with decades-old traditions, and without directly attacking Romney, he hinted that the front-runner is the choice of the party elites.

“CPAC was founded to challenge the Republican establishment,” he said, recalling a famous speech by then-California Gov. Ronald Reagan in 1974.

Gingrich later added, “For the Republican establishment, managing the decay is preferable to changing the trajectory because changing the trajectory requires real fights and requires a real willingness to roll up sleeves and to actually take on the left.

“And that's why the Republican establishment, whether it's in 1996 or in 2008, can't win a presidential campaign, because they don't have the toughness, they don't have the commitment, and they don't have the philosophy necessary to build a majority in this country.”

Gingrich’s wife, Callista, took on a speaking role introducing her husband, and a campaign spokesman said she will be doing more speaking in the coming weeks. Typically Callista Gingrich is a constant but mostly mute presence at his side. This time she spoke humorously about his poor golf game and inability to carry a tune.

“Newt is very committed to our grandchildren and the future of our country,” she said. “We believe in all our hearts that America is the last bastion of freedom. We believe our current path puts the future of our great nation in jeopardy. And we believe bold solutions and fearless leadership are necessary to rebuild the America we love.”

Explaining why Callista Gingrich would be deployed more, campaign spokesman R.C. Hammond said, “Callista certainly does bring out the softer side, the grandfather side of him.”

Many of Newt Gingrich's stump lines were well-received as he assailed President Barack Obama for recent actions such as not approving the Keystone XL oil pipeline and “waging war on religion” through actions such as forcing religious institutions to provide health insurance coverage that includes contraceptives, a decision Obama partially reversed Friday.

CPAC is a three-day yearly gathering of conservative activists in Washington that has long been a crucial stop on the presidential campaign trail.

Santorum, fresh off victories in Colorado, Minnesota and Missouri on Tuesday, was the first of the three contenders to speak Friday as he noted his consistent CPAC presence. The former senator from Pennsylvania said he is the only contender who has consistently opposed universal health care, never believed in man-made global warming and never supported bailouts of Wall Street firms.

Santorum said Republicans had lost touch with core values, leading to a Democratic takeover of government that began in the wave election of 2006 -- in which he lost his Senate seat by 18 percentage points.

“I think we have learned our lesson," Santorum said, "and the lesson we have learned is we will no longer abandon and apologize for the principles that have made this country great for a hollow victory in November.”

Romney is the front-runner with a campaign built for a long march to the nomination, but the Republican base still has its doubts.

Romney attempted to assuage them by incorporating the word “conservative” into his speech at least 19 times -- including describing his term as Massachusetts governor as “severely conservative.”

“I had the unique experience of defending our conservative principles in the most liberal state in our union,” he said.

Romney also emphasized that -- unlike his opponents -- he has never worked in Washington.

“This election really is a battle for the soul of America,” he said. “And it’s going to come down to a choice between whether we want to be a nation of and by Washington or a nation of and by a free people.”