One last thought - isn't it interesting that the scariest bad guys are those who are extremely polite?! Bester and Morden share that trait, and the contrast to their actions is deeply disturbing because of it.
I edited the above post some because it was a pretty confusing jumble of thoughts before. But did anyone else wonder just how much this leader of the Underground Railroad telepaths knew about the assassination plot (i.e. that he at least knew who the target was), once it was revealed, in this episode, that he was a telepath? Since it was revealed very early on that teeps can inadvertantly hear thoughts, even when blocking them out, if they are strong enough and thus "shouted" loudly enough? (Remember the episode soon after Talia and Susan meet, when she "hears" Susan thinking of her mother when the subject of her opinion of Psi Corps is brought up, and explains she couldn't help but hear it. And we see other examples of this phenomenon later.)
Turns out the guy in Downbelow who first pointed Garibaldi to the conspirators in Chrysalis was a teep, and probably a very powerful one. Now given that he saw that informant as he was running to warn the command topside (he told Garibaldi that something was really scaring him), one wonders if he actually heard in his thoughts that "they are going to kill the President" (we know that, even when blocking the stray noise of others' thoughts their minds hear, that if the thought is particularly strong it's like a "shout" they can't ignore). He may have, and not shared them for fear of revealing his telepathic abilities. But then one wonders if he couldn't have just told Garibaldi that the guy told him this, rather than thought it. But even that might have ended up drawing more interest and attention to him, possibly endangering the whole Underground Railroad. He wanted to stay as far off the radar as possible, and didn't trust authority too much--and who can blame him really.
So, tough dilemma this guy may have had. Especially given that the beneficiary of this would-be coup, Clark, was the Psi Corps' political favorite and would likely make them stronger and more dangerous. If he read the paper and knew that, of course.