Not long after news spread that Senator John McCain had been diagnosed with an aggressive brain tumor, his opponent in the 2008 presidential election took to Twitter to share his feelings: 

"John McCain is an American hero & one of the bravest fighters I've ever known. Cancer doesn't know what it's up against. Give it hell, John."

Despite losing the 2008 election, McCain notably came to Obama’s defense several times on the campaign trail.

Obama was also public with his admiration of Sen. McCain despite philosophical differences.

On a 2013 appearance on the "Tonight Show" Jay Leno asked, "Is it me, or do I see kind of bromance with you and John McCain?" Obama responded:

"He is willing to say things regardless of the politics. The fact that he worked hard with a group of Democratic and Republican senators on immigration reform, they passed a bill in the Senate that will make sure that folks who are here illegally have to pay back-taxes and pay a penalty and get to the back of the line, but over time have a pathway to citizenship, and make sure that we're strengthening our borders. He went ahead and passed that even though there are some questions in his own party. So I think that he deserves credit for being somebody who is willing to go against the grain of his own party sometimes. It's probably not good for me to compliment him on television."

Other statements of support were issued throughout the night by the White House and his colleagues as well as former president Bill Clinton and George H.W. Bush: