A few weeks ago, President Obama's most likely scenario for re-election was facing a moderate Republican who had made few controversial remarks in his years in public life and could easily cast himself as a business-focused technocrat.

But that potential opponent, former Massachusetts Gov. Mitt Romney, is no longer the heavy favorite to win the GOP nomination. And the emergence of Texas Gov. Rick Perry could be the best thing to happen to the president's re-election prospects in months.

For all of Romney's faults, from a lack of charisma to a reputation for flip-flopping, he has completely centered his campaign on Obama's most obvious weakness: the terrible performance of the economy under the president's leadership. Romney has essentially said nothing interesting or controversial on any other major issue, but instead has spent all of his time on the campaign trail blasting Obama for the high budget deficit and increased unemployment rate under his leadership.

This approach, reminiscent of how Bill Clinton campaigned in 1992, could be a winner at a time when the electorate, particularly the critical bloc of independent voters, is obsessed with the economy.

Perry, on the other hand, has a much greater visceral appeal to conservatives, but one that brings more risks in winning the middle. He talks tough, as he showed earlier this week by effectively accusing Federal Reserve Chairman Ben Bernanke of treason.

He's openly religious and willing to talk about his opposition to gay marriage and other cultural issues. And he has adopted the Tea Party's positions, including its sharply anti-government rhetoric, promising Saturday in his announcement speech to work "every day to make Washington, D.C., as inconsequential in your life as I possibly can."

If Perry won the nomination, the contest between him and Obama would not simply be one in which the Republican railed against the president's record on the economy and Obama had little grounds on which to attack the Republican. Unlike Romney as candidate, a Perry candidacy would allow Obama's team to highlight the Texas governor's more controversial history: remarks about Texas seceding from the union, his push to require sixth-graders to get vaccines for cervical cancer, his links to George W. Bush, his description of Social Security as a "Ponzi scheme." And Perry, as illustrated by his remarks since he got into the race, doesn't simply want to have an election on Obama's record; he wants a broad debate about the overall role of the federal government.