The comments came in a conference call with the Cruz campaign's National Prayer Team, as transcribed
by Texas Tribune reporter Patrick Svitek.
"Be full of faith and so full of joy that this team was chosen to fight a long battle," Heidi Cruz said. "Think that slavery -- it took 25 years to defeat slavery. That is a lot longer than four years. ... We're going to keep moving forward."
Cruz's campaign did not immediately respond to a request for comment on her remarks.
The comparison was part of a series of statements Heidi Cruz made to buck up supporters after her husband left the presidential race last week in the wake of a dismal finish in Indiana's GOP primary.
She emphasized that Ted Cruz returns to the Senate with an "enormous agenda," per Svitek, and said the work continues.
"We are not only keeping this band together, we have been having meetings five hours a day since the time we dropped out," she said, adding the leadership team of the campaign will continue working.
She said the decision to drop out came in part as losing the next nine states in a row would be "demoralizing" for the campaign, but said the campaign did have a lasting effect on the race.
"It was our first national race, but we have changed the Republican Party by Ted being in the Senate and by him running," Heidi Cruz said. "This party is now being deceived, but the old battles are behind us, the new ones are before us."