ABC News' David Muir, Michael Falcone and Emily Friedman report:
DETROIT - Standing on the 30-yard line of Detroit's Ford Field, Mitt Romney delivered what was billed as a major economic speech before a crowd of about 1,200 supporters on Friday.
In his crucial home state of Michigan, Romney reiterated his new tax plan to applause from an audience dwarfed by the scope of the stadium that seats up to 80,000 spectators.
The Romney campaign promised an economic policy speech on filled with major new policy initiatives, but as it turned out, the venue may have been too big for his message. The supporters, sitting in folding chairs on the field of the indoor football stadium that is home to the NFL's Detroit Lions, were surrounded by tens of thousands of empty seats.
"I want to thank the folks at the Ford Field for making this space available for us," Romney said. "I guess we had a hard time finding a large enough place to meet and this certainly is."
As Romney spoke, campaign advisers acknowledged Romney must score in Michigan. Romney could survive a Michigan loss mathematically, but the political price would be catastrophic.
"What could we change here at this point, " a chief strategist with the campaign told ABC News. "We're all in."
The strategist would not predict the outcome of Tuesday's primary. The campaign source added, if we lose, "We get back up and start campaigning again like we always do," recognizing the tight race here against Rick Santorum.
As Romney celebrated the auto industry indoors, outside protestors gathered with a giant banner with an amended headline from Romney's 2008 New York Times Op-Ed. Protestors changed Romney's "Let Detroit Go Bankrupt," to "Let Romney Go Bankrupt."
The host organization for Romney's speech, the Detroit Economic Club, changed the event site from a downtown Detroit hotel to the field because, as a spokesman for the club told ABC News, tickets sold out within hours. However, not all of chairs set up between the end-zone and the 30-yard line ended up filled.
The outsize venue drew ridicule from the Twittersphere. Conservative commentator Laura Ingraham tweeted twice:
"The pictures of an empty Ford Field are not helping Romney. Poor staging and tepid response from hometown crowd." and "Query: Why move the event to a larger venue when it looks like Romney would not have been able to fill a smaller one?"
She was just one of many pundits and political observers to note the poor optics.
Romney, in his home state where his father ran an automobile company and served as governor, began and ended his speech noting his love for cars. But when he listed his cars, even that turned into an awkward moment.
After declaring Detroit should be "the motor city of the world," Romney said. "I drive a Mustang and a Chevy pick-up truck. He then said his wife Ann drives a couple of Cadillacs.
Before ending his remarks, Romney added, "I used to have a Dodge truck so I used to have all three covered."
ABC News' Christine Romo contributed reporting.