How many lone wolf widows do you think there are going to be among 15-30 million newly uninsured Americans?
This is a serious question, I don't think Republicans have considered at the moment, but they should.
Desperate people with absolutely nothing to lose can be very dangerous.
As a serious note, speaking from my counter-insurgency experience, this is basically the worst possible situation.
The hardest threats to identify and track are individuals with no strong affiliation. It's easy to throw everyone in the Black Panther Party or who lives on a compound in Montana in a registry and put up red flags when they start buying guns and ammo or items that can be broken down into chemical components for improvised explosives. It's easy to intercept traffic between organized groups of malcontents and react appropriately.
It's very, very hard to figure out which cancer patient has suddenly become suicidal due to viewing themselves as a financial liability to their family and is going to express that outwardly rather than privately. It's very, very hard to tell when a father who loses his son has borne a lifelong vendetta that runs contrary to his previous associations and affiliations.
And, to be perfectly blunt, it isn't practical to prevent these kinds of attacks, even with increased security. We've had (many) presidents take bullets from lone, deranged gunmen, and the level of security that can be offered to members of Congress when they're away from DC isn't even a laughable fraction of that. They're creating a threat they can't actually see coming and can't really stop.
The fact they're doing this while the intelligence community is being hamstrung by partisan in-fighting and an intentional obstructive/oppositional administration does not help.