Susan Walsh/AP - San Antonio Mayor Julian Castro (with his brother, Texas Democratic Rep. Joaquin Castro behind him) testifies on Capitol Hill on Feb. 5 before the House Judiciary Committee hearing on immigration.

Congress’ formal legislative debate on immigration opened Tuesday with a hearing in the House, where partisan cracks on the difficult issue emerged almost immediately.

Democrats on the panel focused on the need for a comprehensive overhaul that would expand legal avenues for immigration, improve enforcement of new laws and a path to eventual citizenship for the estimated 12 million people living in the country illegally.

But a number of Republicans who sit on the Judiciary Committee, a key gateway to any new immigration law, questioned whether there might be a middle ground between deportation of those here illegally — long the goal of many in their party — and extending citizenship.

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