The Democratic candidate is yet to publicly announce her position on the new emails published by WikiLeaks
Clinton aides weighed having the Democratic candidate say she opposed the pipeline in a closed-door union meeting, leaking it to news media outlets or including it without fanfare in a policy fact sheet, the emails show.
Clinton eventually announced that she opposed the pipeline on Sept. 22, 2015, at a town hall event in Des Moines, Iowa, early in the contest to win the Democratic presidential nomination. President Barack Obama, also a Democrat, announced that he too opposed the project on Nov. 6, 2015.
The WikiLeaks group released its latest batch of apparently hacked personal emails of Clinton campaign chair John Podesta on Wednesday, just weeks before the Nov. 8 presidential election in which Clinton is facing Republican Donald Trump.
Whether Clinton would oppose TransCanada Corp's pipeline to bring Canadian crude tar sands oil to refineries on the Gulf of Mexico was a major issue in her Democratic primary race against chief rival U.S. Senator Bernie Sanders, who opposed the project.
Clinton was walking a fine line on supporting or opposing the pipeline. The Keystone XL controversy put at odds labor unions, which thought the project would spur job creation, and environmentalists, who advocated moving away from tar sands-derived oil to cleaner forms of energy.
Clinton's decision was further complicated by the fact that the pipeline approval process began when she was Obama's secretary of state from 2009-2013. She said repeatedly that she would wait to announce her position until after the State Department had repeated its review of the project, in deference to her former boss. Privately, aides were figuring out the best way to announce her opposition to the project.
"We are trying to find a good way to leak her opposition to the pipeline without her having to actually say it and give up her principled stand about not second-guessing the President in public," speechwriter Dan Schwerin wrote on Aug. 7, 2015, in one of the apparently hacked emails.
Schwerin was responding to a suggestion by Clinton Campaign Manager Robby Mook that they could use the Keystone announcement to draw news media attention away from Clinton's use of a private email system while she headed the State Department.
The Clinton campaign has declined to verify the authenticity of the Podesta emails released by WikiLeaks. Podesta told reporters on Tuesday that the Federal Bureau of Investigation had notified him it was investigating the "criminal" hack of his emails as part of a broader probe.
The White House last week formally accused Russia of hacking Democratic Party organizations in an effort to influence the presidential election, a charge Russia has denied. As a result, Clinton campaign officials and supporters have warned that such email releases could include fraudulent or misleading documents among genuine emails.
There was no evidence to indicate that the Keystone emails - which provided insight into the campaign's struggle to announce Clinton's position on a major Democratic issue that could put her at odds with the White House - were not genuine.
Clinton's campaign considered having the former secretary of state address the Keystone issue in a private meeting with a building trades union, then immediately roll out a fact sheet on her infrastructure proposals and publish an opinion article on the topic, the leaked emails show.
But Clinton spokesman Brian Fallon thought it might be easier to forgo including Keystone in the policy rollout, skip the opinion piece and have Clinton state her opposition in the union meeting.
"I think we could seem consistent with our past statements about not wanting to get ahead of POTUS on Keystone if her position merely leaked out of the meeting," Fallon wrote in a Sept. 8, 2015, email, using an acronym for the president. "That would seem like a private comment that she didn't intend to become public."
"Perhaps we could just issue an infrastructure fact sheet" without mention of Keystone, "and rely on the (Clinton) Keystone (position) to leak, either organically or with an assist from us," Fallon added.
After Clinton warned at a New Hampshire campaign event on Sept. 17, 2015, that she could not "wait too much longer" and was "putting the White House on notice" that she would soon tell voters her position, Podesta checked in with White House Chief of Staff Denis McDonough.
"Trying to calibrate whether we are threading the needle ok with you guys after Valerie getting her nose out of joint on Keystone," Podesta wrote in a Sept. 20, 2015, email, in an apparent reference to Valerie Jarrett, a senior adviser to Obama.
Podesta said that Clinton's "comments on being frustrated with the delay" were not a "frontal attack" on the president.