President Obama this week praised Homeland Security Secretary Janet Napolitano for her efforts to fight illegal immigration, but she remains the most unpopular member of the president's Cabinet.

A new Rasmussen Reports national telephone survey finds that 43% of Likely Voters have an unfavorable impression of the former Arizona governor, including 24% with a Very Unfavorable opinion of her. Just 23% view the former Arizona governor favorably, with six percent who regard her Very Favorably. One-out-of-three voters (34%) don’t know enough about Napolitano to offer any kind of opinion of her. (To see survey question wording, click here.)

These findings show little change from early March. In early December 2008, just after Obama nominated Napolitano to her current position, 30% of voters had a favorable opinion of her, while 25% did not. But 43% didn’t know her well enough to voice an opinion.

Napolitano has since been criticized for controversial airport security measures and what many feel is a half-hearted effort to stop illegal immigration. The president in the same speech in which he praised the Homeland Security secretary encouraged Congress to move forward on immigration reform, saying his administration has “strengthened border security beyond what many believed was possible." But just 30% of voters think the U.S. border with Mexico is even somewhat secure, while 64% disagree and say it is not secure.

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The survey of 1,000 Likely Voters was conducted on May 11-12, 2011 by Rasmussen Reports. The margin of sampling error is +/- 3 percentage points with a 95% level of confidence. Field work for all Rasmussen Reports surveys is conducted by Pulse Opinion Research, LLC. See methodology.