The pipeline would transport up to 800,000 barrels of oil per day to Gulf Coast and Midwest refineries, much of it for export. Advocates contend the pipeline would be more energy efficient than transporting the oil by truck or rail.
But the opponents, especially those in Nebraska, are organized and politically diverse. Hundreds of ranchers and landowners have challenged the idea of a foreign-based corporation seizing land in the United States.
"No foreign corporation should ever be able to come through and take your property without a permit," said Susan Dunavan, who owns 80 acres of native prairie in southeast Nebraska and is a conservative Republican.
Meanwhile, Abbi Kleinschmidt and Jenni Harrington, who are liberal Democrats with a family farm on the pipeline route near Benedict, complain that a pipeline would undercut the fight against global warming.
"It's about awareness and acceptance of climate change," Sierra Club lawyer Ken Winston, of Lincoln.
Other landowners also worry about risks to the Ogalala aquifer, the vast underground shallow water table that is the state's primary water source.
Opponents have been approaching landowners to persuade them not to accept TransCanada's money to allow access. They are also holding meetings in towns along the route, airing television ads, mailing letters to the White House and trying to meet with members of Congress.
Last week, opponents who met at Thompson's house discussed the possibility of protesting the new route because it crosses land thought to contain Ponca Indian artifacts.
The variety of people in the group helps in brainstorming the campaign, they said.
"Being brought together really opened people's eyes. We're all more similar than we may have thought," said Zack Hamilton, a thick-bearded organic farmer.
But the obstacles to success have grown since the State Department's draft report on March 1 finding no evidence the pipeline would have significant environmental impact along its 1,700-mile run.
"We're going to fight this, to the very end if we have to," Thompson said.