WASHINGTON — U.S. Rep. Kathy Castor expected obstacles as she prepared to lead a new congressional committee to confront climate change.

A president who calls global warming an “expensive hoax.” A Senate led by a cheerleader for coal. A country still divided over science that is long-since settled.

But the first challenge to Castor’s committee leadership did not come from Republicans. Rather, a new generation of environmental activists caught Castor off guard by demanding a committee untainted by campaign contributions and by calling for a “Green New Deal” that would move the country to 100 percent renewable energy by 2035.

These newcomers have forced the Tampa Democrat to defend a previously unquestioned environmental record.

The tension reflects the fight in Washington between Democratic leadership and a wave of young progressives. It also demonstrates the stakes of this new panel. Many on the left view it as Congress’ last best chance to pull the world from the brink of environmental collapse.

“Everything that Kathy Castor does needs to be in line with that or she will be selling our generation short,” said Stephen O’Hanlon, spokesman for the Sunrise Movement, backers of the Green New Deal.

Castor, 52, has the support of House Speaker Nancy Pelosi, longstanding conservation groups like the Natural Resource Defense Council, and local activists who say she has championed environmental causes since her time in local government.

“We’ve got a new group of Young Turks who are making their mark and challenging the establishment,” said Frank Jackalone, director of the Sierra Club Florida, “and I just think (Castor) is the wrong target. She’s as progressive as they are.”

Castor, now in her 13th year in Congress, embraces the challenge and the criticism. In an interview in her Washington, D.C., office earlier this month, Castor vowed to “move forward aggressively” on a green agenda to rapidly reduce carbon emissions and prepare American cities for rising sea levels.

“If I look back a few years from now and we haven’t moved the needle at all, then someone else should take a turn,” Castor said. “But I’m not going to rest until we make true progress.”

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Castor grew up in Tampa in a house of political and environmental activism. Her mother, former Florida Education Commissioner and University of South Florida President Betty Castor, and father Don Castor founded the watchdog group “Save Our Bay” in the 1970s, when Tampa Bay was the final destination for the region’s sewage.

In the early 1970s, Betty Castor was the only Hillsborough County commissioner to support the outspoken leader of the county’s environmental agency when he exposed local water pollution on CBS’ 60 Minutes without authorization.

Kathy Castor graduated from Florida State law school in 1991 and joined the Florida Department of Community Affairs, the defunct agency that once regulated development in the state. She later worked as a private land-use and local government attorney from 1994 to 2000. Castor followed her mother’s political path in 2002 by getting elected to the Hillsborough County Commission.

The Democratic commission shifted drastically in 2004 when conservation icon Jan Platt retired and Republicans took over. Developers, stymied for years by Platt — aka “Commissioner No” — quickly pushed for new construction.

Castor helped beat back a development on a gopher tortoise habitat near the Little Manatee River and pushed for faster cleanup of a toxic spill at a Honeywell plant. More often, Castor waged lonely battles to fight sprawl and was outmatched and overshadowed by big Republican personalities on the commission: Jim Norman, Ronda Storms and Brian Blair.

“As long as Kathy was on there she was able to carry over some of that legacy from Jan Platt,” said Hillsborough County Commissioner Pat Kemp, then Castor’s legislative aide. “She knew land use, she knew the law, and she made the best cases for what could move forward.”

“We won a few, and lost many.”

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In her first ad for Congress in 2006, Castor boasted she went toe-to-toe with TECO after the electric utility put poles in Tampa neighborhoods without warning.

“Sometimes standing up for people means putting your foot down,” Castor said.

If the company was offended, they didn’t show it. TECO donated $1,000 to her campaign that year.

Castor has received about $73,000 from energy and natural resource companies during her 12 years in Congress, according to campaign finance watchdog Open Secrets, including $16,000 from TECO and its employees.

It’s a relatively modest sum for someone who has raised $6.1 million in seven campaigns. Only the defense industry has contributed less to Castor than energy companies.

The political contributions have caused some climate activists to question her commitment to fighting carbon pollution.

“The biggest impediment to actual climate change is money from fossil fuel companies that bankroll both parties in Congress,” O’Hanlon said.

Since 2011, Castor has also invested with her husband in Franklin Utilities Fund, a mutual fund of holdings in large public energy companies. The asset was valued between $50,001 and $100,000 as of 2017, according to a financial disclosure report, and is one of several dozen boilerplate mutual funds in the couple’s portfolio.

Activists have called on Castor and Pelosi to deny a seat to any lawmaker who receives campaign contributions from fossil fuel companies.

Asked if she would follow that rule, Castor stumbled, first telling the Huffington Post it would be a violation of the First Amendment, and later walking that back.

Castor told the Tampa Bay Times she would no longer accept any contributions from energy companies to “set an example.”

“I may have taken for granted that folks understood my record,” Castor said. “I’ve got to prove it.”

Castor’s proponents say she should be judged by her actions. In Congress, Castor has voted with the League of Conservation Voters 93 percent of the time, according to the organization’s congressional score cards.

One of her first co-sponsored bills in Congress raised emission standards on U.S. vehicles to 35 miles per gallon. It became law. She voted for American Clean Energy and Security Act, the most ambitious proposal to tackle climate change to pass the House in the last 20 years. It set up a cap-and-trade system to limit carbon emissions and required energy companies to produce 20 percent of their electricity from renewable sources by 2020. It failed in the Senate.

Castor pushed to punish BP for the Gulf oil spill and has repeatedly filed bills to permanently ban drilling off Florida’s coast. She applauded the Paris Climate Agreement and supported President Barack Obama’s plan to curb carbon emissions from coal plants. President Donald Trump has since moved to rip up both.

“I can’t emphasize enough that she’s the strongest possible environmental advocate,” said Richard Garrity, former executive director of the Hillsborough County Environmental Protection Commission. “She will make a great spokeswoman for all the things the committee has to deal with so we can get decisions based on true science.”

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Soon after Democrats won back the House last November, climate activists staged a sit-in inside Pelosi’s office. They demanded a committee solely focused on the Green New Deal with broad legislative and subpoena powers. Newly elected New York Rep. Alexandria Ocasio-Cortez joined the protest.

Pelosi instead reprised the climate committee as it existed when Democrats last controlled the House. She put Castor in charge, choosing a party loyalist with seniority on the House Energy and Commerce Committee over a progressive rising star, and declined to empower the committee to write bills or call in Trump administration officials.

Rejecting those demands made the committee “weaker” that even its predecessor, Ocasio-Cortez said on Twitter. “Even in our own party, it‘s apparently too controversial to ask that we keep oil+gas co’s away from enviro policy,” Ocasio-Cortez wrote. “There is still time to strengthen it. For all our sake, I hope that we do.”

Castor said the committee would follow the “spirit” of the Green New Deal and assume the projections set forth in federal and international studies that found that global temperature is already 1.8 degrees Fahrenheit warmer than it was 100 years ago. The studies said it will take drastic intervention in the next 12 years to keep the earth from warming to 3.6 degrees above the pre-industrial level. If it gets that high, scientists predict life will change as we know it.

Gary Yohe, professor of economics and environmental studies at Wesleyan University, said there is one way to reduce emissions at levels that avoid that fate: a carbon tax.

Dozens of economists — including former Federal Reserve chairs Paul Volcker, Ben Bernanke, Alan Greenspan and Janet Yellen — published an op-ed in the Wall Street Journal last week calling on Congress to enact a carbon tax that increases every year and rebate it to taxpayers. Yohe said a $45 fee per metric ton of carbon is necessary today, though it would have been $20 had Congress acted a decade ago.

Yet despite that unanimity from the former Fed chairs, it’s not clear if Castor would support a carbon tax. When the Times sent Castor a list of 10 policy proposals for fighting climate change, including a carbon tax, her office wouldn’t say which, if any, she supported.

Still, Yohe said Castor shows great promise.

“Until (Pelosi) announced the creation of this committee, I was not particularly optimistic anything would happen until 2021 and scared to death it wouldn’t happen until 2025,” Yohe said. “The committee chair is very skilled, very knowledgeable, very experienced. I’m very optimistic that at least they will stir things up in the House.”

Times Senior News Researcher Caryn Baird contributed to this report.