Former Massachusetts Gov. Mitt Romney formally announced his 2012 presidential bid Monday, saying it's time to restore America's greatness and move on from failed policies.

Romney lost the Republican nomination in 2008, but has been a favorite among GOP leaders for the upcoming election.  In Monday's announcment, he focused on the economy and criticized President Barack Obama's leadership.

"It is time that we put America back on a course of greatness, with a growing economy, good jobs and fiscal discipline in Washington," Romney said in a video posted on his website, on Facebook and on Twitter.

"Across the nation, over 20 million Americans still can't find a job or have given up looking," Romney continued.  "How has this happened in the nation that leads the world in innovation and productivity? The answer is that President Obama's policies have failed."

Romney is the second major Republican candidate to form a presidential exploratory committee. Former Minnesota Gov. Tim Pawlenty also recently announced his bid.