Democratic presidential contenders Hillary Clinton and Bernie Sanders will face off Thursday night at 9 pm EDT in a critical debate ahead of the April 19 New York primary.

CNN says the debate in Brooklyn—the fifth one-on-one between Sanders and Clinton, but the first since Miami on March 9th—”could be the feistiest yet.”

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As NPR‘s Tamara Keith noted Thursday, in the lead-up to debates, “it sometimes seems like candidates are planting bread crumbs hoping the moderator follows them.” She offered fracking as an example, pointing to Sanders’ recently released “No Fracking Anywhere” advertisement.

Indeed, 350 Action predicted Thursday afternoon that “fracking is expected to be front and center as [the] candidates meet in New York.”

The Hill reported on Wednesday that “Sanders has taken a firmer line against the drilling practice than the Democratic front-runner, calling for it to be banned nationwide.” That’s important, the publication explained, because “[a]nti-fracking forces in New York are more organized than elsewhere in the country.”

Meanwhile, said 350 Action spokesperson Linda Capato, Jr., “Clinton has ramped up plans to tackle climate change, and yet she’s still referring to natural gas as a potential bridge fuel. Tonight’s debate will be pivotal for candidates to take strong stances against fossil fuel interests. No matter how you slice it, natural gas is a fossil fuel, and the only safe place for fossil fuels is in the ground.”

The candidates might also tackle the issue of nuclear power, given that the Indian Point plant is just 25 miles north of New York City. Sanders has called for the accident-prone plant to be shut down, while Clinton has called for increased oversight but not closure of the facility.

Clinton is leading in recent polls of New York voters, but Sanders has been closing the gap. One recent poll showed him trailing Clinton 52-42 percent, up from 55-34 percent last month.