Nancy Reagan has gone on record in "full and complete support" of President Bush's re-election, despite his opposition to embryonic stem cell research.
Reagan spokeswoman Joanne Drake says: "The campaign is certainly about more than one issue."
Nancy Reagan believes stem cells, the body's building blocks, have potential to repair organs or treat diseases such as diabetes, Parkinson's and Alzheimer's, the disease her late husband suffered from.
But many opposed to abortion are against such research because stem cells are typically removed from days-old human embryos that are later destroyed.
Bush's sharp restrictions on federal funding of stem-cell research prompted the Reagans' son Ron, to speak at the Democratic Convention in support of stem cell research. He asked a national TV audience to "cast a vote" for it in November.