The former senator will make it even more official next week, he said.
Brown launched his exploratory committee on March 14. So-called "exploratory committees" are generally only symbolic steps toward running, and federal law doesn't distinguish them from a candidate officially entering a race. So Brown has technically been a candidate since he launched the committee.
That said, his announcement Wednesday erases any doubt that he would follow through and actually run against Shaheen, who is now a GOP target this year.