Nardelli, a Catholic, told the National Catholic Register that she had watched the party drift away from her values and her faith. She pointed specifically to statements by Biden and Obama endorsing "gay marriage" as motivating her decision to leave.
Several former Democrats also criticized the party's continuing support for abortion, as well as religious freedom concerns sparked by a mandate issued recently by the Obama administration.
The Health and Human Services mandate will require employers to offer health insurance plans that cover contraception, sterilization and abortion-inducing drugs, even if doing so violates their consciences.
Texas state representative J.M. Lozano switched parties in March, citing his "pro-life" values as one reason for doing so.
Former Alabama Congressman Artur Davis, a Democrat who had previously supported Obama, revealed in a May 29 blog post that if he were to run for office again in the future, "it would be as a Republican."
Davis explained that the party's agenda has changed, particularly since Obama took office, and said that he no longer feels aligned with its positions.
Among the reasons he cited for cutting ties with the Democratic Party was the contraception mandate, which contradicted his belief that "faith institutions should not be compelled to violate their teachings because faith is a freedom, too."
In explaining his decision to leave the party, Sherriff Waggoner said that ultimately, he believes his choice was in the best interest of the nation.
"We have to make a return to the morals, to the traditional values that this country was founded on," he said. "If we're going to preserve our country, we're going to have to preserve our families. And we're not going to preserve our families going the route that they want to go."