OXON HILL, Md. — Sen. Rand Paul promised a crowd at the Conservative Political Action Conference on Friday that he will soon "propose the largest tax cut in American history."

"I propose we cut everyone's taxes, from the richest to the poorest," Paul said.

Paul's senior adviser Doug Stafford did not have further details to offer on Paul's tax-cut proposal, but said it would be ready in "a few weeks."

As Paul gears up to run for president, with plans to make his candidacy official in early April, he has had no problem attracting support from libertarians, who showed up Friday as usual to cheer Paul at CPAC.

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But tailoring his message to a broader Republican audience has presented more of a challenge. Pushing for lower taxes, a well-loved cornerstone of Republican policy, might help him square that circle.

He didn't need to moderate his message Friday, however. Paul spoke to an audience of devoted, libertarian supporters who populate CPAC each year. He hit on many favorite libertarian topics, including opposition to NSA spying and term limits for congressional lawmakers and federal judges.

Asked what he could choose if he could make one amendment to the Constitution, Paul replied, "term limits," without missing a beat.

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But Paul wasted little time criticizing President Obama, as many CPAC speakers have and will. Instead, he trained his fire on former Secretary of State Hillary Clinton, the likely nominee for president.

Paul has been among the most aggressive, and least coy, likely candidates for president thus far, and he is already a reliable critic of Clinton among likely Republican candidates for president.

At CPAC, Paul continued to critique the former secretary of state.

"Hillary Clinton's abdication of responsibility" to prevent the attacks in Benghazi, Libya, "should forever preclude her from higher office," he said.

Paul added, "It's time for Hillary Clinton to permanently retire."