By Caren Bohan WASHINGTON (Reuters) - When Jim DeMint announced in December that he was leaving the U.S. Senate to head the Heritage Foundation think tank, he said he thought he could wield more influence outside rather than inside the Congress. Any doubt about that may have been put to rest on Monday with the release of a study by the foundation lambasting a bipartisan immigration proposal in the Senate as a budget-buster that would cost taxpayers trillions of dollars.

WASHINGTON - A bipartisan Senate immigration bill would cost the government a net $6.3 trillion over the next 50 years to provide benefits for millions of people now living in the U.S. illegally, the Heritage Foundation said in a report Monday, setting off a fierce dispute with fellow conservatives who attacked the study as flawed and political.

Former US vice presidential candidate Sarah Palin took center stage to speak before conservative activists Saturday, needling President Barack Obama and even fellow Republicans. "We don't have leadership coming out of Washington, we have reality television, except it's really bad reality TV, and the American people tuned out a long time ago," Palin told the Conservative Political Action Conference, known as CPAC, held near Washington.

US Republican Senator Marco Rubio mounted a fierce criticism of China Thursday as it named its new president, saying the Asian giant tortures its citizens, uses forced labor and is bent on global superiority. Rubio, a rising political star seen as a possible 2016 presidential candidate, offered his critique at the conservative policy conference CPAC, where he said communist Beijing's goal was to surpass US influence. "While we are bickering (about budget and tax and spending policies), there is a nation trying to supplant us as the leading power in the world," Rubio warned.