The intensifying Capitol Hill skirmish over whether and how to extend a White House-backed payroll tax cut is opening a potential second front for a partisan battle over environmental riders that have dominated a tense year of divided government.

House Republicans upped the ante yesterday by indicating that their proposal to keep the lower Social Security tax rate for workers would include language fast-tracking the Keystone XL oil pipeline and blocking U.S. EPA's new regulations for industrial boilers (E&ENews PM, Dec. 5).

The emergence of a new vehicle to handcuff Obama administration environmental policy comes as appropriators in both chambers continue hammering out a massive omnibus spending bill that can clear its way into law with less than two weeks remaining until current government funding runs out on Dec. 16.

"The riders are problems -- we know that," the Senate's chief appropriator for EPA and the Interior Department, Jack Reed (D-R.I.), said yesterday of the "thoughtful" talks he and his House counterpart, Rep. Mike Simpson (R-Idaho), are holding.

Reed added that he and Simpson "both thought that it would make sense to reach" agreement on overall funding levels for the agencies covered in the $27 billion-plus Interior-EPA measure before discussing the riders. But Reed declined to confirm that negotiators have yet to progress to talking riders, as Simpson said last week.

The injection of policy provisions into the new House Republican payroll tax plan adds fresh uncertainty to the political debate over which riders might survive in a final package with less than a week remaining until appropriators are poised to release their omnibus. The GOP's battle with Democrats and environmentalists ultimately could come down to one catch-all bill that resolves the payroll tax, government spending for fiscal 2012 and other high-profile expiring provisions such as energy tax cuts.

"It was always likely to come down to one final spending bill" at the end of 2011, Natural Resources Defense Council (NRDC) government affairs director David Goldston said of the climactic riders battle. "The fact that it might also be a spending-and-tax bill doesn't really make it harder or easier. To some extent, the fact that these are measures the public really wants and members really want to get done with helps our case."

The first test of groups such as NRDC's ability to stiffen Democratic spines against environmental riders could come after the House GOP passes its pending payroll tax plan -- if the pipeline and anti-EPA provisions are enough to overcome burgeoning resistance from conservatives. Sen. James Inhofe (R-Okla.) yesterday said that there is a "good possibility" his colleagues could force a test vote on the House plan in the upper chamber, though an exact game plan remains days away.

Liberals are already plotting pushback against the GOP's plans to push White House sign-off on Keystone XL, a $7 billion Canada-to-U.S. link decried by conservationists opposed to the higher emissions of the oil sands fuel it would carry. Sen. Bernie Sanders (I-Vt.), a leading critic of the pipeline, said yesterday that he is working on "a way to respond very vigorously" to the House majority as soon as today, though he declined to "speak for others" in the Democratic caucus whose support for the pipeline is being hotly sought by Republicans.