Reagan was particularly hands on in matters of personnel, both on the campaign trail and in the White House, Lichtman said. While her husband of 52 years, President Ronald Reagan, was a great communicator and leader, his strength did not lie in administration, he said.
Nancy Reagan was also important in persuading her husband to issue a "half apology" in a speech about the Iran-Contra affair, he said. Some viewed those remarks as saving his presidency following the scandal over U.S. arms sales to Iran in order to arm anti-government groups in leftist Nicaragua, he added.
The former first lady also encouraged Reagan to pursue arms negotiations with the Soviet Union that are seen by many as a prelude to the end of the Cold War, Lichtman said.
Former Texas Sen. Kay Bailey Hutchison, also a Republican supporter of stem cell research, said Monday she spoke personally with Nancy Reagan about the issue when she took it up toward the end of her life.
"She never stopped being committed to doing something that she thought was right for our country, and I think the accolades that she is receiving right now are so deserved," she told "Squawk Box" in a separate interview.
Reagan took care of her husband throughout his battle with Alzheimer's disease.
In a 2004 speech in which she broke with Republican opposition to stem cell research, she said, "Ronnie's long journey has finally taken him to a distant place where I can no longer reach him. We can't share the wonderful memories of our 52 years together, and I think that's probably the hardest part. Because of this, I'm determined to do what I can to save other families from this pain."