1. Criminals don't stand in line to fill out background check forms!I think the GOP just played into Obama's hand. This is all about 2014. Every Republican who voted against this is going to have Willie Horton style ads running that will say, Senator (R) voted to make sure that criminals can continue to buy guns. That will be far more devastating a line of attack than the GOP would have been able to make if it had passed.
2. Criminals will never be affected by the background checks and or registration!
These Republicans will be lauded as heroes for upholding the United States Constitution.
Go for the Mental Health angle, that needs fixed!