Transcript for Threat levels raised in all 50 state capitals
The threat level tonight elevated not just in Washington but in all 50 U.S. Capitals with the National Guard activated in several states. ABC's Trevor Ault is in Lansing, Michigan, where armed protesters gathered today. Reporter: Tonight, in cities across the country, a stunning show of force, heavily armed law enforcement surrounding state capitols, bracing for potentially dangerous demonstrations. You know, you hope for the best. You prepare for the worst, and clearly we're prepared. Reporter: Ten states activating their National Guard. Michigan, one of several closing down their capitol. The National Guard and police substantially outnumber the demonstrators here today, but they're going to remain on high alert. There's going to be a heightened law enforcement presence at the capitol until at least mid-february. When they stormed the capitol, when they murdered a police officer, when other people were injured, that's when things go across the line, and that's not going to happen here. Reporter: The FBI putting all 50 states on notice for possible violence on inauguration day. Today small crowds of trump supporters protesting in half a dozen states, many of them armed but peaceful. How long are you going to keep protesting? As long as it takes. The rest of my life if I have to. Trevor Ault joins us outside the Michigan state capitol in lancing. Law enforcement is already noticing the impact of Twitter cracking down on conservative conspiracy theorists? Reporter: That's right, Tom. Police tell me that because some of these profiles have been deleted, it's harder for these groups to organize now. However, it has also slightly hindered law enforcement's ability to gather intelligence about any of those potential plans, Tom. Trevor Ault for us, Trevor, thank you for that.
This transcript has been automatically generated and may not be 100% accurate.