MUSKEGON, Mich. - After several days of sticking to social issues, and sometimes being called to clarify controversial statements, GOP presidential hopeful Rick Santorum came to Western Michigan preaching a purely economic message, focusing on energy and manufacturing.

"Skyrocketing gas prices may put a halt to the improving economy - such that it is," Santorum said. "It's not going to take much to slow down this little train."

Santorum pledged to open ANWAR to drilling, approve the Keystone Pipeline and allow for more hydrofracking to tap domestic natural gas reserves.

He again clarified his recent comments about President Obama's "theology."

"I was criticized the other day. I don't know if you saw Bob Schieffer's show ['Face the Nation' on CBS]. I was criticized [for saying] that the president has radical environmental ideology, even theology," he said. "It's one that puts man just like any other species out there. The Earth is the objective. We focus on the Earth and we don't worry about man. … We believe man has dominion over the Earth and is steward of the Earth… Man has an obligation to protect Earth, be good stewards."

Santorum subtly jabbed Mitt Romney, but did not mention him by name, suggesting it was hypocritical for the former Massachusetts governor to have supported the Wall Street bailout, but not a bailout for Michigan's auto industry.

"Other folks competing here in Michigan supported the financial bailout of Wall Street but not bailout here of auto industry," he said. "I was opposed [to the bailout] on principal, but also from experience. To be for one [bailout] and not the other, you have to explain that to me."

He did, however, name Romney surrogate billionaire Donald Trump, who will campaign in Michigan for Romney.

"I get a kick out my 'friend' Donald Trump. I put 'friend' in quotes," Santorum said "He says of me, 'He can't win, he failed his last race.' Oh, I guess Donald has never failed in anything."