In July, Hillary Clinton released a climate change "fact sheet" that set out ambitious goals for a makeover of the North American economy in the name of solar power. She also has set a more aggressive target for carbon emissions reduction than her former boss Barack Obama.

But critics on both the left and the right have accused her plan of being heavy on rhetoric and low on detail, and many are angered by her dodging of sensitive issues such as the approval of Keystone XL pipeline and Arctic drilling.

The key to Clinton's election campaign is to position herself as the hero of the American middle class. This is why her briefing is littered with references to job creation and "protecting the health of American families." It is a sign of the times that all Democratic contenders — and some tentative Republicans have made climate change a cornerstone of their political vision.

Clinton's bold plan is to position the U.S. as "the clean energy superpower of the 21st century." So far, her policy proposals set out only broad goals. The two headline policies are the installation of more than a half-billion solar panels across the country by the end of her first term, and a mission to power every home with renewable energy within 10 years of taking office.

Obama has come under heavy criticism for his failure to take action on Keystone and Arctic drilling, as well as for his apparent pandering to the fossil fuel lobby as the EPA produced study after delayed study on Keystone's environmental impacts. His 2012 bill to end oil and gas subsidies was killed by Senate Republicans.

Obama's stance has come to be know dismissively as the "all of the above" approach. However, he has overseen a significant cultural change in the attitude toward fossil fuels and climate change as well as significant leaps in energy efficiency.

What Clinton hopes to do is step that process up a notch, without putting at risk a U.S. economy that has boomed on the back of shale production and created jobs for the middle class families she champions. It also means breaking the back of America's obsession with inefficient personal vehicles and road trips, against a backdrop of low fuel prices.

However, she has seen her lead in the polls diminish as she is threatened on the left wing of her party by Bernie Sanders. Martin O'Malley, who currently lags at the bottom of the Democratic polls, goes further and aims for a country powered completely by renewable energy by 2050. Both Sanders and O'Malley are vigorously opposed to the approval of the Keystone XL pipeline, designed to carry tar sands production from Canada's tar sands to the U.S. Gulf Coast.

The noisiest criticism of Clinton comes from her demurring on the Keystone question, seen by climate campaigners as the most important symbol of a candidate's willingness to fight tough political battles on behalf of the global climate. Obama has been demonised for his vacillations on the question. When questioned, Clinton has deftly passed the buck to the incumbent, saying that "this is President Obama's decision, and I am not going to second-guess him."

Keystone alone, while a useful rallying cry, is something of a distraction. Simply vetoing a pipeline will do little to change the supply-and-demand dynamics for fossil fuels, without complementary policies to create fundamental changes in the energy mix. However, Clinton risks alienating anti-fossil fuel campaigners who plead on Twitter to #keepitintheground, and will be disappointed by her reluctance to address the issue of supply.

In the coming months, Clinton will also have to clarify her position on the controversial issues of drilling in Arctic and the removal of the U.S. crude export ban.

If the Democrats come to power, America's oil industry can expect a less favorable tax environment for fossil fuels, regardless of the final candidate. Clinton, whose proposals are more modest than others, recognizes the narrowing window for action on climate change by describing it as an "existential threat."

Oil and gas producers will be monitoring comments on the crude export ban with particular attention. On this question too, Clinton has hesitated. She has said she would support lifting the 40-year ban only as part of a "broader plan" that included concessions from the oil and gas industry. Republican candidates Donald Trump and Ben Carson both assure they would lift the ban.

Clinton's experience of the art of political compromise as Obama's Secretary of State means she is well placed to strike a careful balance between taking a stand on the sensitive issues of the environmental legacy left to future generations of U.S. citizens, and not alienating the business community. She is no alien to the realities of political office.

However, the recent election across the Atlantic of bearded radical Jeremy Corbyn as leader of the U.K. Labour Party, where he pummeled his more moderate, compromise-oriented opponents with his refreshing authenticity and clear ideals, should serve as a warning. Sanders is no Jeremy Corbyn, and Clinton enjoys greater dominance in the Democrat race than any contender of Corbyn's, but she will need to call on all of her skills in the careful art of politics to be everything to everyone.