WASHINGTON >> Republican Mitt Romney took the first official steps toward a second presidential bid Monday, telling supporters he had formed an exploratory committee to begin a White House run.

Romney, who has been planning a second run since losing the Republican nomination in 2008, focused in his announcement on the economy and what he described as President Barack Obama’s failed policies.

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

He criticized Obama’s stewardship of the economy and offered a preview of his expected campaign theme: Romney is a proven business executive while Obama remains unqualified to lead.

“Across the nation, over 20 million Americans still can’t find a job or have given up looking,” Romney said.

“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. He and virtually all the people around him have never worked in the real economy. They just don’t know how jobs are created in the private sector.”

Romney, a businessman who ran Salt Lake City’s Winter Olympics, has lined up donors, staff and advisers for his second presidential bid. He lost the GOP nomination to John McCain in 2008.

Since then, Romney has written a book on government and has raised money and campaigned for Republican candidates.

His strengths are substantial: He’s well known and he’s an experienced campaigner. He has a personal fortune and an existing network of donors. He has a businessman’s background and a record of turning around failing enterprises in a time of economic turmoil.

But his challenges are big, too. They include the health care law that was enacted in Massachusetts on his watch and that’s similar to Obama’s national health overhaul, which conservatives despise. He also must overcome a record of changing positions on social issues, shifts that have left conservatives questioning his sincerity.

He’s the closest thing to a front-runner in a field that lacks one.

The former venture capitalist invested more than $40 million of his own money into the 2008 race and counted on early wins in Iowa and New Hampshire that never materialized. He tried to run to the right of the pack but couldn’t persuade GOP primary voters to overlook his reversals on social issues including abortion and gay rights. He also struggled to allay skeptics of his Mormon faith.

Romney, who in his first presidential race struggled to explain to Republicans why he would give the party the best chance to win the White House, is arguing this time that he would be the strongest to challenge Obama on the country’s single biggest issue.

In his under-three-minute announcement video, recorded Monday at the University of New Hampshire, he underscored what is expected to be his overarching campaign theme.

“From my vantage point in business and in government, I have become convinced that America has been put on a dangerous course by Washington politicians, and it has become even worse during the last two years,” Romney said. “But I am also convinced that with able leadership, America’s best days are still ahead.”