“In politics, admitting you've changed your mind is not something most people like to do. But here it goes. I have decided to seek re-election to the United States Senate,” Rubio said in a statement this morning.
"I have often said that the U.S. Senate can be a frustrating place. And it's true. After witnessing the gridlock that grips Washington, I think just about every American – Democrat or Republican – would agree. But the Senate is also a place from which you can perform great services for the people you have the honor of representing," he said.
Rubio tweeted that he made up his mind over Father's Day weekend. Still, just a month ago, he insisted that he would not be running for a second term.
"In November 2016, I will either once again be a private citizen or I will be the next president of the United States," Rubio said last October during his presidential bid.
The move puts an end to months of pressure from fellow Republicans to consider running for the seat. With several seats at risk this year in key swing states like Pennsylvania, Florida and Ohio, the GOP is trying to protect its slim majority in the Senate.
A Quinnipiac University poll released this morning showed Rubio leading both of the main Democratic contenders for the seat in head-to-head matchups. Republican candidates hoping to replace Rubio trailed their likely Democratic rivals.
ABC News' Ines DeLaCuetara contributed to this report.