The chairman of the Senate Homeland Security and Governmental Affairs Committee said that the United States is “certainly vulnerable” to the Islamic terrorist group ISIS.

Senator Ron Johnson (R-WI) said those who support ISIS see them as a “winning organization” so the U.S. has no other choice but to completely defeat the group.

“The best strategy the U.S. can employ to defeat this is actually defeat ISIS in Iraq and Syria so that the reality is conveyed that this is not a winning organization, it is a losing organization,” Johnson said on CNN’s “State of the Union” on Sunday.

Johnson cited the recent failed attack on a cartoon contest in Texas as an example of ISIS supporters seeing them as “winning” despite the attack failing in its goal.  Johnson said it’s also difficult because they can’t easily deal with those who are activity promoting ISIS.

“The problem is, what do you do with the not-guilty-yet? We do have laws, we have a Constitution, and it’s extremely difficult for law enforcement officials when you might have tens of thousands of sympathizers — how do you track them all?” Johnson asked.

Johnson said that up to 90,000 twitter accounts in the United States were promoting ISIS although Twitter has begun to delete them.

FBI Director James Comey said Thursday that the terrorists are trying to recruit “hundreds, maybe thousands” of potential terrorists in the U.S.  Former Homeland Security Secretary Tom Ridge said the U.S. is in “more serious circumstances today than we were after 9/11.”

“Remember, back then we thought about al-Qaeda in Afghanistan and Pakistan and a few other places? Well, we’ve seen al-Qaeda metastasize,” Ridge told CNN. “It is now a global scourge. And you have the ascendancy of ISIL. The combination of those two groups — their appeal to the lone wolfs and we see them acting in Belgium and in France and in Canada and the United States, so the threat factors and the nature of the threats are far more complicated and far more serious today than on Sept. 12, 2001.”