Carolyn Kaster/AP

Obama's Last Hope for Climate Change: EPA

The president is getting serious about regulatory changes.

President Obama is ready to take one more shot at combating global warming with the last, least-popular, and messiest tool he's got left: regulations administered by the politically besieged Environmental Protection Agency.

It won't be popular, it might not work, and it could cost him his pick to head EPA.

But the hard reality is this: Three years after Congress killed a cap-and-trade bill, Obama is running out of time.

If Obama doesn't finalize EPA rules controlling greenhouse-gas emissions from the nation's carbon-emitting power plants before he leaves the White House, a Republican president or Senate could undo the rules—and his legacy.

"He is serious about making it a second-term priority," Heather Zichal, Obama's top energy and climate adviser, said at an event last week. "He knows this is a legacy issue."

In a speech at Georgetown University on Tuesday, Obama will outline a timeline for EPA to move forward regulating carbon emissions from new and existing power plants, which account for almost 40 percent of the country's heat-trapping emissions. EPA proposed rules for new plants last spring but missed its April deadline to finalize them.

But Obama will immediately faces hurdles in Congress, even as he seeks to unilaterally impose regulations through the executive branch. The Senate has not yet confirmed Gina McCarthy, Obama's nominee to head the agency who is currently EPA's assistant administrator for air. Obama's announcement Tuesday will further inflame McCarthy's already incendiary confirmation process.

"The Obama administration may conclude that the policy priority of moving forward on GHG emissions reductions outweighs the political gain of confirming McCarthy in a timely manner," according to analysis published Monday by ClearView Energy Partners, a Washington-based nonpartisan consulting firm. McCarthy could execute Obama's directive from her current post as EPA's top air chief. Acting Administrator Bob Perciasepe could remain in his post indefinitely, which is allowed under EPA's organizational plan.

As a result of the administration's environmental activism, Obama's party may also face newfound trouble in the 2014 midterms. The National Republican Senatorial Committee is already targeting vulnerable red-state Democrats up for reelection, including Sens. Mary Landrieu of Louisiana, Mark Begich of Alaska, and Mark Pryor of Arkansas. "Landrieu Ushers in Obama's Climate Change Agenda," says one NRSC statement released Monday. "Jobs & Economy Fall Victim to Liberal Wishlist." GOP strategists believe that voters in Republican-leaning, energy-producing states could punish Democratic incumbents who support additional regulations.

"In what amounts to a national energy tax, the president will pivot away from jobs—the No. 1 issue for constituents," said Don Stewart, spokesman for Senate Minority Leader Mitch McConnell, R-Ky. McConnell will be criticizing the president's plan in a floor speech Tuesday morning.

If Republicans win back the Senate next year, they will have the tools to undo any new regulations. Using the Congressional Review Act, senators would be able to bypass the majority leader and force a vote requiring only 51 votes to pass a resolution nullifying regulations finalized within 60 days. The White House is reportedly worried such an effort could succeed against EPA's climate rules.

"He [Obama] is concerned about whether or not he has enough support in the Senate to defend vetoes of environmental regulations," said Michael Kieschnick, CEO and cofounder of CREDO, a cell-phone company heavily involved in advocating for action on climate change. Kieschnick has attended private fundraisers with Obama in recent months where the president addressed climate change.

Amid these political obstacles, Obama must navigate the significant legal and policy hurdles, which will inevitably come along with a regulation whose wide-reaching scope surpasses any other EPA rule, according to experts.

"Two years is about the minimal time it would take to go from soup to nuts on a rule like this," said Roger Martella, who was EPA general counsel under President George W. Bush. "These rules don't come out of the clear blue sky and involve lengthy internal deliberations before the public even gets a first peak at them."

Once EPA is done writing the rules, a flood of lawsuits will pour in from both sides of the issue. Litigation also takes time, during which it would be ideal if Obama was still in the White House. "We reason the Obama administration wants to defend its power plant GHG … rule(s) against legal challenges rather than leaving it to another, potentially less simpatico administration," states the analysis by ClearView Energy Partners.

Time might be the biggest hurdle of all.

"Part of the challenge is, how much can they do in a limited amount of time," said Jody Freeman, who worked on energy and climate issues in the White House during Obama's first term. "This plan is a race against time. We're already six months into a second term."