He believes the court's four liberal-leaning justices showed their support for the insurance mandate during the questioning, while the four conservatives, including Chief Justice John Roberts, displayed their skepticism about its constitutionality.
"That leaves Justice [Anthony] Kennedy as the swing vote," said Lee. "Based on his questions, his demeanor, his facial and body language and the questions being asked and answered, I think he's leaning in the direction of the conservatives."
Utah Attorney General Mark Shurtleff and his chief deputy John Swallow were in the chamber, part of a large group of attorneys general representing the 26 states that filed suit against the 2010 law, and they agree with Lee's prediction.
"We all feel pretty strongly it will be a 5-4 decision," said Shurtleff, one of six attorneys general representing the plaintiffs during the hearing.
Shurtleff said he saw Kennedy as an ally based on his first question to the solicitor general, which was "Can you create commerce in order to regulate it?"
Utah's attorney general has observed a few Supreme Court hearings before but felt awed by the historic nature of this week's proceedings and he believes others in the courtroom had similar feelings.
"The justices understand that this is one of the most significant cases in the last 50 years or more," he said.
If the court does strike down the insurance mandate it could topple the entire law, which is President Barack Obama's signature domestic achievement. And the court is expected to rule in June, just as the presidential contest heats up.
The politics surrounding the event were on display outside the court, where hundreds of liberal activists clashed with a smaller group of tea party supporters in dueling protests.
Danai Lamb from California flew to Washington to participate in the rallies because she wants everyone covered by insurance.
"I believe that women who cannot otherwise afford it should have good health care and family planning," Lamb said. "The right wing is trying to tear it apart and I don't think it could work effectively if it's torn apart."
On the other side of the argument were people like Sherry Burrows of North Carolina who believes that if the Supreme Court upheld the law, it could give Congress nearly unfettered power, the same position espoused by Utah's elected officials.
"If they can do this, then they can force us to do whatever. Today it's our health care, tomorrow it's going to be where we live, what we eat," she said. "It's a lot bigger than just health care."
The historical significance of the hearings was evident, as everyone from U.S. Attorney General Eric Holder to Senate Minority Leader Mitch McConnell, R-Ky., attended the second of three days focused on the health law, the longest oral argument for one case in 45 years.
The first day focused on whether the states had standing to sue since the mandate doesn't go into effect until 2014, though the justices signaled that they are ready to move forward now. The third day of hearings will explore whether the rest of the law can survive if the mandate is struck down and whether the expansion of Medicaid to low-income childless adults steps on states' rights.
Laura Schmitz contributed to this report