REUTERS/Brian Snyder
Republican presidential nominee Mitt Romney and former Florida Governor Jeb Bush (L) pose for a photograph together after a 2012 Romney for President campaign rally in Tampa, Florida October 31, 2012.
Romney, the former Massachusetts governor who lost to President Barack Obama in the 2012 election, commended Bush for "follow[ing] his family's pattern of putting country above himself."
"His campaign has been about answers to real problems and about policies to strengthen our country," Romney said in a statement posted on his Facebook page.
"It has been a campaign conducted in the finest tradition of dignity and integrity and Jeb Bush gave it his all: he can have no regrets. I am proud to call him a friend," Romney added.
Bush suspended his campaign Saturday night after a disappointing showing in the South Carolina primary.
He entered the process as the favorite to win the Republican nomination, but his campaign lost momentum throughout the summer and fall, as real-estate mogul Donald Trump's campaign unexpectedly took off. And low-polling Republican candidates have faced pressure from their party to drop out so that establishment donors can consolidate support behind an alternative to Trump.
At the time he left the race, Bush had 8.3% of the vote in South Carolina with 58% of precincts reporting, putting him in fourth place behind the projected winner, Trump, and the two candidates battling for second place, Sens. Marco Rubio and Ted Cruz.