The Keystone XL Pipeline has emerged as a major issue in the Massachusetts special U.S. Senate election, with environmental groups committing nearly one-third of the $1.25 million in outside money already spent on campaigns.
The biggest spender so far is the League of Conservation Voters, which has already spent more than $545,000 to help elect Democratic candidate and Rep. Ed Markey, who has a strong pro-environment platform.
“Our field campaign is resonating with voters across Massachusetts,” said Navin Nayak, a political specialist for the group. “The people of Massachusetts want climate change champion Ed Markey representing them.”
The group also plans to spend about $100,000 more to knock on the doors of more than 240,000 likely Democratic primary voters before the April 30 primaries.
Supporters of the Canada-to-Texas pipeline are urging the Obama administration to approve the project to create thousands of jobs and make the United States less dependent on foreign oil. However, critics say drilling for oil in Canada’s dirty tar sand will release greenhouse gas emissions.
Markey faces fellow Democratic Rep. Stephen Lynch in the party primary and holds a double-digit lead, according to most polls. The winner will face the top vote-getter in the Republican primary that features former U.S. Attorney Michael Sullivan, state Rep. Daniel Winslow and businessman Gabriel Gomez.
The general election is June 25, for the open Senate seat of Democrat John Kerry.
Another environmental group spending big money to defeat Lynch is the NextGen Committee, which has reported spending more than $196,000, according to Federal Election Commission filings.
The group is backed by California billionaire Thomas Steyer, who has called on Lynch to oppose the pipeline. NextGen has spent $54,700 for an aerial banner that read "Steve Lynch says: Go Habs! And Go Canadian Dirty Oil."
The banner appears to question Lynch’s loyalty to the Boston Bruins. The "Habs" is the nickname for the Montreal Canadiens. The banner was flown over downtown Boston ahead of a matchup between the two hockey teams.
NextGen also spent more than $50,000 for video mobile billboards and $40,000 for online advertisements. That's an apparent violation of an agreement signed by Lynch and Markey known as the "People's Pledge," which is designed to discourage radio, television and Internet ads by outside groups. If there is a violation, the candidate who benefits agrees to pay half the cost of the ad to a charity named by their rival.
Markey has made environmental issues one of his top priorities and the focus of a television campaign ad that highlighted his role in holding BP responsible for the 2010 oil spill in the Gulf of Mexico.
Another big supporter of Markey is the Service Employees International Union, which has made more than $368,000 in independent expenditures to help elect him. The money went to cover gas, staff salaries and canvassing services.
The group making the biggest push on behalf of Lynch is the International Association of Firefighters, which has reported spending more than $85,300, including money for gas, tolls, rally signs, car rentals and travel expenses.
Lynch worked as an ironworker for 18 years and, along with Markey, has appealed to unions for their support.
None of the independent expenditures reported to the FEC by the end of the week were made to either support or oppose the three Republican U.S. Senate candidates -- former U.S. Attorney Michael Sullivan, Norfolk state Rep. Daniel Winslow and Cohasset businessman Gabriel Gomez.
League spokesman Jeff Gohringer told FoxNews.com Saturday all of the money has been spent in support of Markey.
The Tea Party-aligned Conservative Campaign Committee, however, has said it plans to spend up to $200,000 on radio and television ads to support Sullivan and target Winslow and Gomez.
Winslow and Gomez have called on Sullivan to renounce the ads by the group, which they say holds extreme anti-gay positions.
The Republican candidates have not agreed to the People's Pledge and argue Lynch and Markey began their campaigns with a stockpiles of money.
The independent expenditures by outside groups give no indication how much each candidate has raised in donations so far. The first reporting filing deadline in the race is April 18, less than two weeks before the primary.
The Associated Press contributed to this report.