Quote source: Brainy Quote
Donald Trump Scores First Endorsement From a U.S. Senator. (The Wrap, 2/28/2016)
And they are particularly unhappy about their Congress. “I told Donald Trump this isn’t a campaign, this is a movement,” Sessions said, promising that Trump would fix the country’s immigration system. “Look at what’s happening. The American people are not happy with their government.”
Only a Presidential candidate with the emotional development of a 12 year old would consider this a "big surprise announcement."