The unofficial theme of the second night of the 2008 Democratic National Convention in Denver was the building of a green economy. In speech after speech, the Democrats pointed to Senator Barack Obama’s plan to put 1 million plug-in hybrid electric vehicles on American roads by 2015—and to rebuild the American auto industry in the process—as the cornerstone of his plan for energy independence.

Early in the evening, Nancy Floyd, a venture capitalist who focuses on alternative energy, made the link between the revitalization of the American economy and the revamping of Detroit. She said that Obama “will cut taxes for families who buy fuel-efficient cars and trucks, and make sure that those cars are being built by American autoworkers.” Michigan Governor Jennifer Granholm hosted a town hall panel discussion to discuss the fate of her state’s work force and Obama’s efforts to create a new generation of “green collar” workers.

These presentations set the stage for the evening’s prime-time speakers, who spoke specifically, and repeatedly, about the potential for plug-in hybrids. “If we actually got ourselves off foreign oil, we can make our country safer. We’ll start to solve global warming,” said Former Virginia Governor Mark Warner. “And with the right policies, within 24 months, we’ll be building 100 mile-per-gallon plug-in hybrid vehicles right here, with American technology and with American workers.”

In a rousing speech, Montana Governor Brian Schweitzer extolled the environmental and economic virtues of energy efficiency. “Barack Obama understands the most important barrel of oil is the one you don’t use.” Schweitzer tied that concept to Obama’s specific proposal to “invest $150 billion over the next 10 years in clean, renewable energy technology.” He said, “Senator Obama’s plan will also invest in a modern transmission grid to deliver this new, clean electricity from wind turbines and solar panels to homes, offices and the batteries in America’s new plug-in hybrid cars.”

While the ability for Obama, if elected, to deliver on his energy-related campaign promises remains to be seen, Tuesday night’s presentations helped establish the “plug-in hybrid” as a mainstream American household term—perhaps as a synonym for “100-mpg vehicle.” The speeches also set a high benchmark for Republicans when they outline Senator John McCain’s energy and environmental policies at the GOP convention next week in Minneapolis-St. Paul.