When a bill to approve the Keystone XL pipeline failed to overcome a Democratic filibuster in the Senate on Tuesday night, it would have been easy to see it as merely a temporary victory for Democrats and environmentalists. The bill got 59 votes (after passing the House easily), and come January, there will be more Republicans in the Senate. Even before the vote, Mitch McConnell made clear that he’ll bring it up again once the new Congress takes office.

Is this a battle the liberals are on their way to winning?

That’s certainly what some environmentalists want to argue. This last election saw a new effort to use election spending as a means of elevating the climate change issue, spearheaded by liberal billionaire Tom Steyer. He spent tens of millions of dollars this year on campaign activities in support of Democratic candidates (most of whom lost).

In recent days I had conversations with two consultants who helped guide Steyer’s efforts: Mike Casey, who represents a variety of environmental groups and green-tech companies, and Chris Lehane, the longtime Democratic operative who serves as Steyer’s chief strategist. Unsurprisingly, they tried to put the election results in the best possible light. But they also made some persuasive arguments about the future of Keystone in particular and the potency of climate change as a political issue in general.

While President Obama hasn’t said explicitly that he’ll veto a bill to build the pipeline, he has been dismissive in recent days about the benefits of the project, and reiterated his declaration from last year that he would only approve it if it doesn’t worsen carbon pollution.

“He has expressed a very appropriate skepticism at the wild job claims that the tar sands lobby has made,” Casey noted, “and also he has talked about this as Canadian oil, not American oil.” As for the argument that whether the pipeline is approved or not the tar sands oil will still be coming out of the ground, and therefore the environmental effects would still be felt even if the U.S. government rejects the project, Casey pushed back hard. “Here’s how we know that’s a lie,” he said, pointing out that the Norwegian company Statoil recently canceled a tar sands project in Alberta because of rising costs, and the fact that there is limited capacity in train cars to ship the oil if they don’t have a pipeline. “The market realities are walking away from this project.”

But let’s accept for a moment that, as harmful as tar sands oil is, it’s only one piece of the climate challenge. Why has it become such a central focus of the debate in America? The primary reason may be that it’s concrete and domestic. The environmental activists who brought so much attention to it were able use it as a means of organizing because there was a clear goal to rally people around: stop the pipeline. It’s much easier to get someone to volunteer their time, write a letter, or make a donation for a focused goal like that than for something more vague, like “we need to reduce emissions by X percent over the next Y years.”

When I asked about that element of the Keystone issue, Lehane agreed that its specific nature made it a natural vehicle for climate activism. He also argued that Keystone was “particularly vulnerable” to a public campaign, because the chief beneficiary is a foreign oil company and the claims that company has made about both job creation and the supposedly limited effect of the emissions haven’t panned out. But beyond that, he argued that “it’s absolutely critical” to translate the broad issue of climate change into “hyper-local issues.” That could mean rising seas in Miami or asthma rates among children in Colorado, so you aren’t talking to people about far-off things like ice caps and polar bears.

Republicans would offer a simple reply: you lost. In most of the races where Steyer put his money, Democrats went down to defeat. That would have happened anyway, of course, but Lehane argues that they knew going in that 2014 was going to be a tough year; the goal was to lay a foundation that could pay dividends in 2016 and beyond, by forcing candidates — including Republicans — to talk about climate and energy. He pointed to newly elected senator Cory Gardner, one of their prime targets, who cut this ad in which he stood in a wind farm and talked about his commitment to clean energy, not something one would expect from a Republican.

Which raises the question of how the 2016 GOP presidential candidates will address the climate issue. It would be an exaggeration to say climate denialism is mandatory in the Republican Party. It’s OK for a Republican to cautiously admit that climate change may be occurring; they just can’t favor doing anything about it. But imagine a primary debate in which the candidates are asked to hold up their hands and say definitively whether they admit climate change is a reality. What would they do? And what might the consequences be? We could see a repeat of the 2011 debate in which the contenders were asked whether they’d walk away from a deal that contained ten dollars in spending cuts for every one dollar in tax increases, and they all raised their hands, which made them look like rigid ideologues who didn’t particularly care about solving problems. On the other hand, candidates with an eye toward the general election might do the unexpected and take a tentative step toward acknowledging the reality of climate change.

What’s more, as this blog has detailed, the U.S.-China deal capping carbon emissions, and the prospects of a global climate treaty coming next year, just as the GOP presidential primary is heating up, make it more likely that candidates on all sides will have to talk about the issue.

“It’s inconceivable to me that you go into 2016 without this being one of the major issues that the campaigns have to talk about,” says Lehane, “and an issue where the Republicans are put at a particularly significant disadvantage, since they’re not even willing to acknowledge that it’s an issue.” He drew a comparison to marriage equality, noting the GOP will begin evolving as soon as they see their position has become a political liability. At that point, the discussion will turn away from whether climate change is happening and on to which solutions are preferable.

“You push a big rock up a pretty steep hill, and it’s slow, but then you get to the top of that and the rock begins to roll,” Lehane says. “There’s a moment when the inertia and the momentum flip, but you have to push the rock.”