As a make-or-break election cycle looms for the Senate, two upper-chamber votes yesterday sketched out a playing field of more than a dozen lawmakers who could be fence-sitters on the nation's biggest energy issues.

Four senators seen as at least somewhat persuadable by advocates and lobbyists on both sides of the environmental divide -- Bob Casey (D-Pa.), Susan Collins (R-Maine), Claire McCaskill (D-Mo.) and Olympia Snowe (R-Maine) -- voted for both a proposal to fast-track the controversial Keystone XL pipeline and to suspend U.S. EPA limits on industrial boiler emissions. Among that group, all but Snowe helped deliver greens a victory nearly one year ago by voting against a GOP plan to strip EPA authority over greenhouse gases.

Eight more senators split their votes on yesterday's two most closely watched environmental proposals, supporting either the pipeline or blocking the EPA rules: Jon Tester (D-Mont.), Kent Conrad (D-N.D.), Scott Brown (R-Mass.), Mark Begich (D-Alaska), Herb Kohl (D-Wis.), Kay Hagan (D-N.C.), Ben Nelson (D-Neb.) and Jim Webb (D-Va.). Another swing-state senator who voted against last year's greenhouse gas push, Sherrod Brown (D-Ohio), yesterday opposed both amendments to the chamber's transportation bill -- which became a vehicle for symbolic votes on measures unrelated to transportation.

Further muddying the political picture was the wild-card status of 10 senators in the group. Snowe, Conrad, Kohl, Nelson and Webb are retiring from Congress this year, while McCaskill, Casey, Tester and both Browns are facing difficult re-election battles, when every vote they take is potential fodder for 30-second campaign ads.

The pressure appeared particularly intense for Tester and McCaskill. Tester, who is facing Rep. Denny Rehberg (R-Mont.) in November, "might as well start packing up his office now" if he comes out against the pipeline, one oil-industry executive predicted before yesterday's vote.

Meanwhile, one of the Republicans vying to take on McCaskill in the fall, former Missouri State Treasurer Sarah Steelman, released one of those ads hours before the Keystone XL vote. Steelman hailed the Canada-to-U.S. pipeline, which would carry up to 830,000 barrels of crude per day, as promising to "completely replace the million barrels of oil a day we buy from" Hugo Chavez's regime in Venezuela.

The National Republican Senatorial Committee joined the fray after the Keystone XL fast-tracking fell four votes short of passage, reminding reporters that President Obama had called Democrats to lobby them against a plan from Sens. John Hoeven (R-N.D.) and Richard Lugar (R-Ind.) that would speed the pipeline. The Keystone XL project has taken on even more political potency in recent weeks as gasoline prices have spiked.

The White House pushed back at such GOP finger-pointing over Obama's support for further environmental review of the 1,700-mile pipeline's still-unsettled route through Nebraska. Obama spokesman Jay Carney yesterday took direct aim at one of the Republicans' favorite -- and hotly disputed -- talking points in favor of the pipeline, calling Hoeven and Lugar's plan "ineffectual, sham legislation that has no impact on the price of gas."

After the votes, Hoeven told reporters that the Keystone XL plan would have won 58 of the 60 senators needed to break a filibuster, counting Sen. Mark Kirk (R-Ill.), who is recuperating from a stroke, as a pro-pipeline vote. "We will continue this fight for a project that the American people want," he added, suggesting that the support of 11 Democrats could help the House GOP push for the pipeline's inclusion in any bicameral deal on a transportation bill.

Green groups hailed the ultimate failure of the Hoeven-Lugar and boiler emissions plans, which made for a good day in their camp when coupled with the approval of a plan to support Gulf Coast restoration and the rejection of an expanded offshore drilling amendment from Sen. David Vitter (R-La.)

"Each senator picked which issues to stand up and fight and which ones to let go," one environmental advocate tracking yesterday's votes said, speaking candidly on condition of anonymity. "I think there would be even more opposition to both boilers and Keystone if it ever came to a stand-alone vote, but there was a package 'win some, lose some' philosophy that some members followed."

Even Casey, who backed both the boiler emissions and XL amendments despite scoring a 91 percent rating last year from the League of Conservation Voters, offered a nuanced response that credited "the concerns on both sides of" the EPA regulations debate. The first-term senator chalked up his votes to a concern for manufacturing jobs already shed in his home state.

Yet beyond the rosy outcome, warning signs are piling up for environmentalists who counted Obama's January rejection of Keystone XL as a major victory.

While House Minority Leader Nancy Pelosi (D-Calif.) yesterday criticized Republican claims that the pipeline's Canadian oil sands crude would help bring down U.S. gas prices, she also acknowledged: "That doesn't mean it might not be something that is worthy of some consideration for reasons other than domestic consumption."

Her Senate counterpart, Majority Leader Harry Reid (D-Nev.), also pointed to the emergence of a two-front debate over Keystone XL that was sparked by pipeline sponsor TransCanada Corp.'s decision to begin building its southern leg without the need for a presidential permit (E&E Daily, March 7).

"Half of the pipeline is already being built, and the company building the pipeline is submitting another application for the remainder of the route," Reid said. "This process should be given time to work."