Just two hours later, Clinton is due back on a different stage to deliver a speech to the League of Conservation Voters – a mainstream environmental group that strenuously opposes Keystone.
The contrasting events illustrate the dilemma facing Clinton, who has declined to take a position on Keystone but who needs support from environmentalists if she pursues a presidential bid in 2016.
Environmentally-minded donors and voters are likely to hold greater sway among Democrats in the 2016 presidential election than they did when Clinton ran and lost in 2008. Her refusal to take a stand on Keystone has disappointed some of the loudest - and richest - environmental activists, who view the project as a litmus test of a candidate's environmental stance.
The brief LCV speech - scheduled to be delivered during a 7:30 p.m. dinner - is Clinton’s first policy-related public appearance since the midterm elections and comes amid growing evidence that Clinton will soon announce whether she is pursuing a White House run.
In isolation, her appearance at the LCV event could be construed as at least tacit opposition to the Keystone project. But her appearance with Landrieu muddies the question: The Louisiana incumbent, who faces stiff odds in a runoff election against Rep. Bill Cassidy (R-La.) on Saturday, says Keystone will help create energy jobs in her state.
Clinton, who also campaigned for Landrieu during the regular midterm season, will address donors paying up to $12,000 a ticket for cocktails at the home of a longtime Clinton supporter. The event is closed to the press.
"We are thrilled that Secretary Clinton is speaking at our event," LCV spokesman Jeff Gohringer said when asked about the juxtaposition with the Landrieu party. The group "has no control over her schedule," he said.
As for Keystone, "I think she will hear our position tonight, which is a great opportunity," Gohringer said.
A spokesman for Clinton said she had no comment on Keystone now.
Although similar projects have gone ahead with little objection, opposing the Canada-to-U.S. pipeline has become a mark of environmental commitment among activists. The State Department has jurisdiction because the pipeline crosses an international border, and Clinton has said her four years as secretary of state make it inappropriate for her to weigh in.
President Obama has said that a State Department review should run its course before a decision is made, and Clinton could be forced to take a side if Keystone remains unresolved far into 2015. She has said she is likely to make up her mind about running after Jan. 1.
Keystone is a stand-in for the increased clout of voters and donors animated by environmental issues. California billionaire and heavy Democratic donor Thomas Steyer, who had pledged to spend $100 million during the 2014 midterms, has been blunt in saying that he has made the pipeline an uncomfortable subject for his own political allies.
Steyer’s spending came in under $100 million, however, and produced few tangible results for Democrats.
Nonetheless, appealing to what one senior Democrat calls the “Steyer wing” may be particularly important for Clinton now, assuming she wants to quietly outmaneuver more liberal potential challengers for the Democratic nomination.
Steyer himself has not publicly endorsed her, although his older brother is a close Clinton ally. Former Bill Clinton White House aide Chris Lehane, a Steyer political adviser, said Steyer is committed to a "multicycle process" and expects to see the same environmental issues resonate in 2016.
Steyer aside, the issues surrounding climate change and energy production and usage have become sharper in many Democratic voters' minds since 2008.
Fracking, viewed either as a potential economic boon or a potential environmental hazard, was barely in the public eye when Hillary Clinton last ran. Although scientists regarded climate change as a fact in 2008, the intervening years have helped settle the issue for a larger percentage of the public, environmental groups say.
"Climate change and energy played a big role in 2012, and we have seen an increase through 2014 and heading into 2016," the LCV's Gohringer said.
His group had record spending of more than $30 million on election-related activities in the midterm cycle, Gohringer said. He declined to give an estimate for what Clinton would raise for the organization Monday.
LCV endorsed Clinton for New York Senate in 2000 and 2006. The group endorsed Barack Obama for president in 2008.