The Environmental Protection Agency will release a proposed rule Monday that seeks a 30 percent cut in carbon emissions from power plants by 2030, sources familiar with the plan confirmed to the Washington Examiner on Sunday night.

The rule also calls for a 25-percent cut by 2020, with both sets of reductions from 2005 levels.

The forthcoming proposal, the details of which were first reported by the Wall Street Journal, is a centerpiece of President Obama's climate strategy and would amount to the most far-reaching EPA effort to tackle greenhouse gas emissions. Coming after years of stalled climate action in Capitol Hill, the move would affect the nation's 1,600 power plants, which account for 40 percent of the nation's carbon emissions that scientists say cause climate change, and could fundamentally change the nation's entire electricity system.

The proposed rule is being executed through the Clean Air Act and likely will face an array of legal challenges. It would be finalized in June 2015, with states needing to submit their implementation plans a year after that. If states fail to submit a plan, the EPA could impose its own.

The proposed rule, which EPA Administrator Gina McCarthy will formally announce Monday, would put the United States well beyond the 17 percent of emissions reductions Obama committed to at the 2009 United Nations climate talks in Copenhagen. It comes as nations are preparing for key negotiations next year in Paris, and Obama has tried to position the proposal as a model to get significant commitments from other big polluters like China and India.

The 2005 baseline year is less ambitious than some environmental groups had hoped. That's because the EPA is looking to allow states to use already implemented policies — such as renewable electricity mandates and energy-efficiency programs — as credits toward meeting the rule, the Journal reported. Using a more recent year would have required steeper emissions cuts, as states would have fewer options to use as credits.

But that baseline is what the electric utility industry had pushed for. It heartened some because it would give them and states more flexibility to meet the standard, though others felt the nearer-term target of cutting emissions 25 percent cut below 2005 levels by 2020 was asking too much.

Twenty-five "percent from 2005 is better as a starting point than what we had been hearing because it will give utilities credit for reductions already achieved since that time," an industry source said in an email.

While the industry and environmental groups will need time to sort out the hundreds-page-long proposed rule, the political impact will be immediate.

It's coming just as the midterm election season is hitting its stride, and will likely be a hot political topic. While some Democrats see that as a good thing, others are less convinced — chiefly, a handful of Senate Democrats running in red-leaning states who worry the EPA is handing their opponents a weapon to wield.

Obama briefed several congressional Democrats on the details Sunday afternoon, and urged them to go on offense to defend the proposed rule, a source familiar with the conversation said. That source said Obama referred to previous federal environmental rules that included industry buy-in — such as fuel-efficiency standards for vehicles finalized in August 2012 and the EPA-led acid rain program — as models for how he envisions the power plant rule working.

"We have a really good case here to make to the American people and we need everyone, we need all of you, to go out there and make that case," the source said, paraphrasing Obama's remarks.

Senate Democrats are forming an attack plan that includes fact checking, floor speeches, state events and social media messaging, a Senate Democratic aide said. On the House side, a Democratic aide said planning meetings have been underway between staff and members for weeks. Environmental groups are getting into the fray as well — the Natural Resources Defense Council, for example, plans to host events in 30 states this month to build support for the rule.

"It's long past time for there to be some limit to the carbon pollution that power plants spew into our skies," said Sen. Sheldon Whitehouse, D-R.I. "It's real and it's serious, but with Republicans in Congress still refusing to take the climate threat seriously, EPA standards are the best we can do to end the polluters' long holiday from responsibility."

But some vulnerable Senate Democrats running for re-election aren't likely to be pleased by the timing. Senate Energy and Natural Resources Committee Chairwoman Mary Landrieu, D-La., and Sens. Mark Pryor, D-Ark., John Walsh, D-Mont., and Kay Hagan, D-N.C. -- who last week challenged her GOP opponent for not believing in man-made climate change and also signed a letter asking EPA to delay the forthcoming proposed rule -- are a few of them. The proposed rule also could batter Democratic challengers in Kentucky and Georgia.

Republicans said they plan to highlight the rule on Capitol Hill. The House Energy and Commerce Committee will likely hold a hearing on the rule, said Charlotte Baker, a majority spokeswoman. Senate Minority Leader Mitch McConnell, R-Ky., also will focus on the rule, hoping to give his colleagues -- and himself -- a platform to slam the proposal.

"The president’s plan would destroy jobs and raise costs for families across America, and Congress must listen to these families — even though the president won’t," McConnell said last week.