President Barack Obama cut short a campaign swing through Florida on Friday and ordered adverts attacking his Republican rival to be pulled from the airwaves, following a deadly shooting rampage in Colorado.
First lady Michelle Obama and Vice President Joe Biden also cancelled their campaign events for the day.
The President urged Americans to "stand together" with the people of Aurora and said political campaigning ahead of the election should be temporarily set aside.
"There are going to be other days for politics. This, I think, is a day for prayer and reflection," he told supporters at the previously scheduled campaign event in Fort Myers, Florida.
"We're going to stand by our neighbours in Colorado during this extraordinarily difficult time," he said.
Obama's opponent, Republican presidential candidate Mitt Romney, also pulled all television adverts in Colorado until further notice.