By Mike Taibbi, NBC News correspondent

If you're on the protesters/security beat in Denver, as producer Mario Garcia and I have been, the question now is: “What's next?”

In the days and weeks before we arrived all the research we could gather about the city's law enforcement readiness amid the prospect of between 25- and 50,000 demonstrators...those were the predicted numbers on the websites of several major protest groups who'd been in contact with the Denver Police Department about their plans...suggested our beat could lead to a storyline that might impact the news generated by the Democratic Convention itself.

Then, on Sunday, there were around a thousand protestors in the first big march on the Pepsi Center. On Monday, around half that number walked along the crowded 16th street mall and then assembled for a “justice rally” in front of Denver's federal courthouse. And last night, perhaps 200 or 300 were involved in the first real “confrontation” with police.

Depending on which side was providing the descriptions, either the police used pepper spray and fixed batons without provocation to move the protestors out of Civic Center Park to the streets near the mall, where arrests were then made; or the protestors, many of them masked... intent on disrupting fundraisers scheduled for several downtown hotels and brandishing rocks or other projectiles...left the park on their own, blocked traffic and defied police lines to invite their own arrests. In the end, around 100 protestors were hit with misdemeanor charges of interference, blocking intersections and refusing to comply with lawful police orders.

There was a tense standoff on the streets that lasted hours, but it didn't lead to any further confrontations; and, overall, the numbers of protesters in town are still much lower than anticipated. Instead of tens of thousands of demonstrators, the city's uniformed presence of some 4500 fully riot-equipped personnel from all over the state had tens of hundreds or even fewer to deal with.

But the thing is... you never know. In fact Mayor John Hickelooper had told us he's a little nervous this week because “you don't know what you don't know.” In this YouTube/cable news world, when everyone with a cell phone or a camera can dominate the news cycle at any time with just the right video or images (or wrong images, if you're John Edwards or George Allen or Michael Richards or any number of now ex-cops caught on tape brutalizing a suspect or alleged suspect), you wonder where even the limited protest presence here might turn. We heard some ugly language last night, and saw that some had aimed their spray paint cans to write some ugly graffiti... "Kill a Cop, " "_______ the Pigs." We've met a few people positively aching for attention.

And as everyone agrees... the police chief, the mayor, and the protest leaders we've been talking to this week... all it takes is a couple of knuckleheads to create a situation that plays out not just as something ugly on camera... but perhaps even tragic.

59-year-old Barbara Cohen, an antiwar movement veteran and co-founder of Recreate '68, one of the biggest protest groups that's been planning for its DNC activities for years, was worried about the prospect of violence, but just as worried about the absence of passion she felt was responsible for the low turnout so far. "I just don't know," she told me, "what it takes to get people fired up anymore. People are so apathetic." And though some were "fired up" last night during the standoff with the police, Cohen doesn't think confrontation and violence are the answer to her movement's inertia. "That just gets you taken off the street," she told me. "And then you can't be heard..."

Anyway now the police and the protesters have engaged each other, and not happily. We watch and listen.