Former Pennsylvania senator Rick Santorum says he is ending his bid for the White House and will support Republican candidate Marco Rubio.

Santorum said Wednesday on Fox News Channel that he is "suspending our campaign as of this moment."

He described Rubio as a "born leader" and praised his "optimistic" message.

Santorum entered the race in May as a heavy underdog in a crowded Republican field featuring more than a dozen high-profile candidates — many of them newcomers to presidential politics.

His longshot status kept him off the mainstage in all of the presidential debates, his campaign never gaining enough steam to put him up against heavyweight contenders like billionaire Donald Trump, Texas Senator Ted Cruz and former Florida governor Jeb Bush.