Rendell said he believes most environmentalists will rally around Obama, despite reports indicating that fossil-fuel interests are outspending green advocates on political advertising this year, a reversal of the pattern from the 2008 election.
"They may not be as wildly enthusiastic as they were in 2008," Rendell told reporters after his speech. "But the last I checked, an enthusiastic vote counts the same as a tepid vote."
Rendell, who promoted legislation subsidizing the growth of renewable energy such as wind and solar projects, encouraged dispirited clean-energy advocates to persevere, despite the unpopularity of their agenda in Republican-dominated Harrisburg.
"Keep pushing, keep making the case and not giving up," he said. "Politics is not for the faint-hearted."
But Rendell also encouraged them to send a message to all Democrats to rein in legislators who fail to support their agenda by withholding financial support to the party committees.
"There have to be consequences," he said. "The problem with most political givers is they have short-term needs, so they continue to support people even if those people turn their backs when the chips are down."
But Rendell also urged environmentalists to show some moderation, particularly toward Marcellus Shale natural gas development, which he said had boosted the state's economy, and was better for the environment than the alternative - oil and coal.
"Everything's a balance," he said. "You have to be cognizant of that. When the environmental community takes positions that to the average person in the public seem to be anti-economic growth, you lose them. You lose them."
Contact Andrew Maykuth at 215-854-2947, @Maykuth on Twitter or firstname.lastname@example.org.