SIOUX CITY Iowa

Republican presidential contender Mitt Romney, seeking to protect his narrowing lead and fend off challenges from rivals in this early-voting state, assailed Mike Huckabee and Rudy Giuliani over supporting tuition breaks and broader sanctuary for illegal immigrants or their children.

As a new poll showed his advantage trimmed in Iowa, the former Massachusetts governor on Tuesday singled out the two Republicans giving chase here and likened them to Democratic front-runner Hillary Rodham Clinton. "There are those people in both parties who are in a sanctuary state of mind, who believe in sanctuary cities, who believe in policies which are sanctuary in nature," he said.

Just weeks before voting begins, the race in the leadoff caucus state has tightened. Romney led in Iowa by double-digits in polls for months but now is trying to curb Huckabee's recent rise in surveys and gains among religious conservatives, while working to prevent Giuliani from mounting a more serious challenge.

Underscoring the fragile state of Romney's lead here, a CBS News/New York Times poll released Tuesday showed Romney with 27 percent backing by likely GOP caucus-goers. Huckabee, the former Arkansas governor, now threatens Romney's lead with 21 percent of support; Giuliani, the former New York mayor, has 15 percent.

Going after both on a salient issue in western Iowa, Romney contended that Huckabee fought for tuition breaks for children of illegal immigrants in his state, while Giuliani provided tuition breaks at the City University for illegal immigrants. He said Clinton, too, backs such breaks.

"Giving a better deal to the children of illegal aliens than we give to U.S. citizens from surrounding states is simply not fair and not right," Romney told reporters during a one-day trip to the state.

In turn, Huckabee said in a phone interview with The Associated Press: "The attacks from a guy who has sanctuary cities in his state is interesting." Huckabee said he backed a bill in Arkansas and would do so again that gave children of illegal immigrants "the opportunity to be awarded for academic achievements" based on merit provided they were in the process of applying for citizenship.