McCain's campaign

Upon seeing the gauges, Obama spokeswoman Linda Douglass said, "You can use it to check all the hot air coming out of [McCain's] Straight Talk Express.

A senior adviser handed out gauges on McCain's campaign plane and they were passed out outside Obama's energy speech in Lansing, Michigan, on Monday.

"They think it's funny that they're making fun of something that is actually true," Obama said Tuesday in Ohio. "They need to do their homework."