Former Minnesota Gov. Tim Pawlenty is expected to open an exploratory committee for the 2012 presidential race today, making him the first in a handful of top-tier Republican aspirants to take the first official step toward a challenge to President Obama.

Pawlenty's move, first reported by the Associated Press, allows him to begin taking contributions and hiring staffers for a GOP primary run, with the first debate among the party's presidential hopefuls less than two months away. The Facebook page of the 50-year-old two-term governor posted a notice this morning inviting supporters to hear a "special message" later today that will outline his plan, the AP reported.

Pawlenty joins two other potential Obama opponents, former Massachusetts Gov. Mitt Romney (R-Mass.) and former House Speaker Newt Gingrich (R-Ga.), in condemning Obama administration emissions limits after previously aligning with the concept of curbs on greenhouse gases.

In 2007 Pawlenty signed state-level legislation that set emissions-reduction targets, but within two years had distanced himself from the effort. By early 2010, he was joining 19 other governors -- including Mississippi's Haley Barbour, another Republican mulling a presidential bid -- in imploring Congress to stop EPA from implementing its emissions regulations (E&E Daily, March 11, 2010).

"There's no question the climate is changing," Pawlenty told NBC's "Meet the Press" in February 2010 when asked about his past avowals that global warming was occurring. "But the more interesting question is how much of that is man-made versus natural causes? ... [W]e should all be in favor of reducing pollution. But we need to do that in ways that don't burden the economy."

Romney and Gingrich have similarly shifted away from previous pro-environmentalist rhetoric in recent years. The former Massachusetts governor opted not to enlist his state in a regional compact to reduce greenhouse gas emissions after initially engaging in talks on the issue, though he described climate change in 2010 as a real phenomenon in which "human activity is a contributing factor."

Gingrich, for his part, is proposing to eliminate EPA and replace it with a more economic-centered "Environmental Solutions Agency," though he has previously warmed to the notion of a carbon-neutral planet (E&E Daily, March 15).