Sen. Lisa Murkowski (R-Alaska) speaks with reporters on Capitol Hill on Oct. 25. (Aaron P. Bernstein/Reuters)

For months, the top Republican and Democrat on the Senate Energy and Natural Resources Committee had worked together to craft a comprehensive energy bill.

But that bipartisan spirit was tested Thursday as Republican Chair Lisa Murkowski (Alaska) and ranking Democrat Maria Cantwell (Wash.) clashed over whether to open the Arctic National Wildlife Refuge to drilling.

ANWR is back on the legislative table — again — because GOP lawmakers are desperately seeking revenue to help pay for a massive package of tax cuts they debuted Thursday. As part of a budget bill passed by the Senate last month, lawmakers instructed committee members to find $1 billion in additional revenue — a maneuver widely seen as designed to open the refuge to drilling. The Senate narrowly defeated an amendment from Cantwell to strip out the refuge language.

With the tax package on center stage in the House, the senators sparred on the other side of the Capitol over whether to allow drilling on one of few undisturbed parcels of land in the United States. The sparring foreshadows the partisan rifts that are likely to divide the upper chamber over paying for a tax package that Republicans need to claim as an accomplishment.

On one side of the debate sat Republicans and virtually every Alaskan elected to statewide office, who argue that opening ANWR to drilling will boost the state's economy and the nation's energy security. Using modern drilling techniques, they argue, it can be done with little environmental impact.

On the other side sat virtually every Democrat, who contend that the region is too ecologically critical to indigenous caribou hunters and the broader Arctic ecosystem to bore for oil.

"For those of us who call Alaska home, to suggest that we would despoil our environment for short-term gain is offensive," Murkowski said.

The committee meeting turned tense at times, with Cantwell pressing her Republican counterpart about why the bipartisan energy bill has been abandoned to take up the ANWR question yet again.

"This hearing is a great departure from the strong working relationship that Sen. Murkowski and I have set to work together on an energy agenda that will move our country forward," Cantwell said.

"I almost want to call this 'caribou for millionaires' because it is the most ridiculous idea I've heard as it relates to meeting the tax reform agenda," she added.

Tucked against the Beaufort Sea in Alaska's North Slope, a 1.5 million-acre coastal plain in the refuge has been part of a heated political debate since the 1980s. In 1989, Congress considered the issue of drilling in the refuge, and the Energy and Natural Resources Committee passed a pro-drilling bill. But it was shelved after the Exxon Valdez ran ashore in the Prince William Sound. In the 1990s, then-Sen. Frank H. Murkowski (R-Alaska), Lisa's father, tried unsuccessfully, again. A 1995 attempt to open the refuge passed the GOP-controlled House and Senate but was vetoed by President Bill Clinton. A group of moderate Republicans defeated a similar attempt in 2005.

Alaska's elected officials turned out in force for the hearing. Rep. Don Young, Alaska's long-serving and lone member of the House, shot back at opponents of the drilling plan, without naming names, for what he saw as their ignorance on Alaskan issues.

"I don't feel too comfortable on the Senate side," Young said. "I need a flashlight most of the time because sometimes it's pretty dark over her."

The hearing was attended by seemingly every Alaskan elected to statewide office, including Gov. Bill Walker (I), Lt. Gov. Byron Mallott (D) and Sen. Dan Sullivan (R), who all supported drilling in the refuge.

During the four-hour meeting, Murkowski and other Republicans emphasized only "one ten-thousandth," or 2,000 acres, of the refuge would be open to drilling if legislation was enacted.

Cantwell and Sen. Angus King (I-Maine) countered that that figure discounts the impact of roads, airports and pipelines necessary to bring the oil out of the refuge and to the state's primary petroleum artery, the Trans-Alaska Pipeline System.

At one point, Cantwell held up a map showing, she said, that drilling "will take up a significant portion of the refuge."

Later, Young offered a rebuttal. "The map that the ranking member showed was actually drawn up by the Sierra Club," he added. "That bothers me. That's old information."

The debate over Arctic drilling also marked one of the few times rank-and-file Republicans seemed comfortable bringing up Russia in 2017 without prompting.

"Producing more energy strengthens our national security," Sullivan said. "It's not just American officials who recognize this," he added. "The Russians know this as well."