If you want a spark, Paul should come out and announce a major press conference. They may suspect he's dropping out, but whatever.
Then have him come out and say that while he's been traveling on the campaign trail, in addition to the thousands showing up to support him, he's been listening to hear and understand the reasons why people are hesitant to support him. From that, he believes that people have misunderstood his foreign policy/national security views.
Then have him give a 30 min speech, (where he doesn't get interrupted after 90 seconds by an interviewer or by a debate buzzer) where he states his views, talks about the moral, Constitutional, fiscal and historical rationale for his views, and most importantly describes how he would still be a strong protector of the country should it still face an attack. Have this speech be pre-written and have him prepare for it and have notes for it. In addition to potentially addressing misconceptions about his foreign policy for hundreds of thousands (if not millions) of people, it can also demonstrate that he's not nearly the bumbling and stuttering speaker that many have come to think of him as.
Do that, and do it right now, when Santorum's rally is stalling and when many conservatives are struggling to find some alternative to Romney, and I think you may just reignite his campaign. At the very least, it reintroduces him and his views back into the conversation about the Republican party, its candidates, and its policies.