Usually when lawmakers stage all-night filibusters, they do so to protest a piece of legislation. Senator Ted Cruz, for example, spoke for twenty-one hours last September in opposition to a resolution intended to avert a government shutdown. Texas State Senator Wendy Davis spoke through the night in August to protest an anti-abortion bill.

The senators planning to take the floor Monday evening, however, are doing so to raise alarm about an absence of legislation. More than two dozen Democrats and two Independents intend to speak from the end of voting Monday afternoon until approximately 9 am Tuesday to call for congressional action to counter climate change.

“The cost of Congress’ inaction on climate change is too high for our communities, our kids and grandkids, and our economy,” Senator Sheldon Whitehouse said in a statement. “On Monday we’ll be sending a clear message: it’s time for Congress to wake up and get serious about addressing this issue.”

Whitehouse has given floor speeches about climate change some sixty times over the past two years, speaking weekly when the Senate is in session. On Monday he’ll be joined by Hawaii’s Brian Schatz, who helped to organize the event; majority leader Harry Reid; Environment and Public Works committee chairwoman Barbara Boxer; and about twenty-four other senators, including independents Angus King and Bernie Sanders.

Congress has not considered any serious climate legislation since the summer of 2010, when a fragile bipartisan coalition supporting a cap-and-trade bill collapsed. Since then, Republicans have grown more entrenched in climate denialism, and have made it clear that any attempt to regulate carbon pollution would fail. Just last Friday, minority leader Mitch McConnell told the Cincinnati Enquirer that he didn’t believe in man-made climate change. “For everybody who thinks it’s warming, I can find somebody who thinks it isn’t,” McConnell said.

Monday’s all-nighter—it’s not technically a filibuster, since no bill is on the table—is part of long-term campaign by the newly launched Senate Climate Action Task Force to heighten the sense of urgency about climate change, and pressure lawmakers to take a more aggressive stance on carbon regulation. The group is playing defense, too, trying to fend off attempts to undermine President Obama’s Climate Action Plan, most significantly the new Environmental Protection Agency rules for carbon emissions from power plants. Without any legislation on the horizon, the initial task for the group is to shift the political climate so that denialism and inaction becomes a liability.

That challenge is evident in the midterm elections. Many of the Democratic incumbents in tight races come from conservative energy states: Mary Landrieu from Louisiana, Mark Begich from Alaska, Mark Pryor from Arkansas, Kay Hagan from North Carolina and Mark Warner from Virginia. They’ve distanced themselves from their colleagues’ climate fight, criticized the EPA’s efforts to regulate carbon pollution, and publically support the Keystone XL pipeline. None are expected to be present Monday night.

But if they want to hold on to the Senate, Democrats have to defend those seats in the midterms. Rather than start an intraparty war as the Tea Party has done within the GOP, the Democratic climate push is focused largely on the right’s refusal to acknowledge man-made climate change, with an eye towards making it a major issue in 2016. Tom Steyer, the billionaire behind climate-focused super PAC Next Gen, said last month that his group is not planning to attack oil-friendly Democrats in the midterms, although it won’t give money to them either. Next week, Senator Whitehouse will bring his climate speech to Iowa, which hosts the first major voting for the presidential nominees.

“Climate change threatens Rhode Island coasts and Iowa farmlands alike, and I look forward to this opportunity to talk to rural Americans about the threats they face,” Whitehouse said in a statement. “I also realize that in order to advance serious climate change legislation in Congress, we need to make climate change a major topic in the 2016 presidential race.”

You can watch the floor dicussion here, and join in on Twitter with the hashtag #Up4Climate.