Senate compromise on guns is a real breakthrough -- yet a tenuous and modest step

Ten Republican senators appear ready to answer pleas from anguished relatives of recent mass shootings to "do something" by defying their own party's dogma on gun reforms.

The group struck a deal with Democrats on Sunday that could lead to more spending on mental health care, school security, extra scrutiny of young gun buyers and incentives to states to temporarily confiscate weapons from those deemed a threat.

Critically, the size of the group of senators brings the promise of overcoming the Senate filibuster, the procedural block requiring 60 votes that has allowed conservatives to thwart previous efforts to pass gun reform legislation. If the package can pass the Senate -- still a massive question given the bill is not yet written and the fierce conservative backlash it's likely to stir -- it would mark the most sweeping attempt to tackle America's epidemic of mass shootings in many years.