Romney fails to elaborate on his 20% tax cut in awkward speech setting where he let slip another gaffe about his wealth

Republican frontrunner Mitt Romney's much-heralded economic speech flopped Friday, overshadowed by a gaffe over luxury Cadillacs and his choice of an over-ambitious venue, the Detroit Lions' football field.

Romney opened himself up to derision for choosing a 70,000-seat stadium which attracted just over 1,000 people, many of them school children bussed in to help fill out the crowd, tucked into a corner of the astro-turf pitch.

The small crowd underlined again his inability to draw large numbers of supporters and to excite the conservative base.

The speech too turned out to be a flop. Having been hyped by his campaign staff all week, Romney had little new to say, particulary about how he planned to pay for the 20% tax cuts he announced earlier in the week.

It will be the picture of the near-empty stadium, contrasting with a much fuller one when Barack Obama was campaigning in February 2008, that will be remembered.

The organisers, defending the venue, said that the original location had been filled within 90 minutes of the speech being announced so they had looked for an alternative, opting for Ford Field.

Romney commented on the vast stadium as began his speech. "I want to thank the folks at the Ford Field for making this space available for us," he said. "I guess we had a hard time finding a large enough place to meet and this certainly is."

Highlighting the smallness of the crowd, his words echoed round the empty stadium seats. He was not helped by the near-silence, winning only an occasional round of applause. At one point, having made a joke about the reluctance of children to leave home, only a handful of people in the audience laughed, an embarrassing response that the empty stadium amplified.

Political opponents quickly waded in. Obama's campaign adviser, David Axelrod, in a tweet, wrote: "Judging from pictures, looks like Mitt pinned himself in inside the 20."

After delivering his speech, Romney made a throwaway remark about cars that will be replayed when the speech itself will have been long forgotten.

In an attempt to ingratiate himself in the motor capital of America and undo some of the damage caused by a call in 2008 to let the car industry go bankrupt rather than be bailed out by the federal government, he listed cars owned by himself and his wife Ann.

He would be a president who loves cars, he said. "I like the fact that most of the cars I see are Detroit-made automobiles. I drive a Mustang and a Chevy pick-up truck. Ann drives a couple of Cadillacs, actually. And I used to have a Dodge truck, so I used to have all three covered."

The remark, in an unscripted moment, will add to the image of Romney as so wealthy he can talk casually about his wife having not one but two Cadillacs. Although two cars are not unusual in American homes, two luxury Cadillacs, which range in price from $35,000 upwards, are not.

It is a mistake on par with his $10,000 bet in a televised debate with Texas governor Rick Perry.

Romney's fumble came on a day in which there was some solace in the polls, with two showing him overtaking rival Rick Santorum in Michigan ahead of the Tuesday primary. A Mitchell Research-Rosetta Stone survey put him on 36%, Santorum 33%, Ron Paul 12% and Newt Gingrich 9%. A Rasmussen poll put Romney on 40%, Santorum 34%, Paul 10% and Gingrich 9%.

Romney's team had billed the Detroit speech as a major economic one that would build on the 20% tax cuts he promised earlier in the week. But he had almost nothing new to say.

He described it as a "bold conservative plan" but failed, in the face of much scepticism about his tax cuts, to say how he planned to pay for them. The one new line was that he planned to raise the age for Medicare from 65.

He reiterated he would balance the budget by handing over many federal programmes, such as Medicare and distribution of food stamps, to states, who he claimed would handle them more efficiently. He would cut subsidies to rail provider Amtrak and groups such as Planned Parenthood.

He has said most of this before. As for the question of how to cut tax and balance the budget, he opted for vagueness rather than detail, saying that if he was president, he would order every federal programme to be scrutinised to see whether it was worth borrowing from the Chinese to support.