|Republican presidential candidate Newt Gingrich addresses guests gathered at pro-life documentary screening [Getty]
Former House of Representatives Speaker Newt Gingrich's status as the front runner for the 2012 Republican US presidential nomination is fading after weeks of attacks by rivals and intense media scrutiny of his political record.
Gingrich acknowledged that negative advertisements by political opponents had dented his popularity but suggested he would refrain from launching his own attacks, while responding more aggressively to criticisms.
"I will be back on a positive basis, I will ... tell you what I stand for and I will answer any question that comes up based on the false and inaccurate advertising of some of my friends," Gingrich told a crowd at a campaign event.
A Public Policy Polling survey of likely participants in the January 3 Iowa caucuses - the first-in-the-nation Republican nominating contest - showed the former House speaker dropping to third place from first in the Midwestern state in the span of a week.
Ron Paul in the lead
Congressman Ron Paul of Texas led the new poll, which was released on Monday.
Gingrich's lead also evaporated in national polling as Republican candidates competed for the right to face President Barack Obama, a Democrat, in the November 2012 US presidential election.
"Newt Gingrich's campaign is rapidly imploding and Gingrich has now seen a big drop in his Iowa standing two weeks in a row," Public Policy Polling, which is affiliated with the Democratic Party, said in a statement.
Gingrich earned just 14 per cent support in the new Iowa poll compared to 22 per cent a week ago and 27 per cent two weeks ago.
Paul took over the lead in Iowa with 23 per cent in the new polls, an increase of five per cent over the past weeks.
Former Massachusetts Governor Mitt Romney, who has been seen as Gingrich's main national rival, was second with 20 per cent.
The survey of almost 600 people, taken December 16-18, had a four per cent margin of error.
Another poll, by CNN/ORC International, showed that Gingrich and Romney were tied with 28 per cent of support nationally from Republicans and Republican-leaning independents.
'World is dangerous'
Gingrich has run an unorthodox campaign, signing books at events and talking about topics ranging from the economy to brain research and lunar mining.
Cary Covington, a professor of political science at the University of Iowa, said, "Ron Paul is just eviscerating Newt Gingrich in the ads".
An onslaught of television and radio commercials by Gingrich's opponents that paint him as unreliable and a Washington insider has taken a toll.
"It's tough not to feel the effects in millions of dollars in advertising spent against you with no comparable response," said Tim Albrecht, spokesman for Republican Iowa Governor Terry Branstad and a former Romney staffer during Romney's unsuccessful run for the Republican presidential nomination in 2008.
Gingrich acknowledged that criticisms aimed at him by rivals - omnipresent on Iowa television and radio - had taken a toll.
"You get enough negative ads before you start answering them, your numbers go down for a while," he told reporters after speaking to a small crowd at Global Security Services, a small business.
He nevertheless took a swipe at his rival, Paul, who has opposed much of US military action abroad, while discussing concerns about North Korea's nuclear capabilities.
"The world is dangerous," he said. "I really stand apart from some of our candidates in believing we need a strong defence."