Firewalls are supposed to prevent unauthorized access to a computer system.
Virginia has served as a political firewall for Democrats in recent election cycles, and the Clinton campaign seemed to make a critical update when it added Sen. Tim Kaine to the national ticket.
But what happens when the firewall develops cracks?
We may be about to learn the answer.
A series of polls show the presidential race between Democrat Hillary Clinton and Republican Donald Trump tightening up, with Clinton still holding a narrow national lead but losing ground in key swing states such as Florida and Ohio and in Colorado, Iowa and Nevada.
The numbers have Democrats worried and Republicans thinking they just might pull this thing off.
Democrats should be concerned.
If Trump carries all the states Mitt Romney won in 2012, he would have 206 electoral votes in his column.