Democrats also have begun embracing a tougher stance on immigration as well.

Democrats have focused on offering opportunity to immigrants, but the study by two think tanks urged them to begin speaking in terms of "requiring" illegal immigrants to become legal and about what's best for the United States.

Many House Democrats have gone a step further, endorsing an enforcement-only bill by freshman Democratic Rep. Heath Shuler of North Carolina that would bolster border security and require employers to verify their workers' legal status with an electronic verification system.

The SAVE Act has drawn 140 co-sponsors, 48 of whom are Democrats, many of them vulnerable freshman who won seats from Republicans.

The Democratic leadership dislikes Shuler's bill. Republican leaders are considering collecting signatures for a special petition that requires House leaders to bring a bill up for debate if 218 members sign.