Former Republican House Speaker Newt Gingrich has announced he will run for the presidency in 2012.
Mr Gingrich, who left elected office in 1999, becomes the best known of what analysts consider a lacklustre field of declared Republican candidates.
Other major potential hopefuls have yet formally to enter the race.
Mr Gingrich is best known for leading a team of conservative Republicans who won control of the US House of Representatives in the 1994 election.
'Returning to hope'
Mr Gingrich, 67, first announced his candidacy on Wednesday through his account on the video sharing website YouTube.
"I believe we can return America to hope and opportunity, to full employment, to real security, to an American energy programme, to a balanced budget," Mr Gingrich said in the video.
Mr Gingrich added: "We've done it before. We can do it again."
In order to "get America back on track", he said US citizens would have to "talk together, work together, find solutions together and insist on imposing solution on those who don't want to change".
Appearing on Fox News on Wednesday evening, Mr Gingrich said he believed President Barack Obama had pushed the "wrong policies that have lead to the wrong outcomes".
"Unemployment is the wrong outcome," he said.
Mr Gingrich said he believed he could beat Mr Obama on a "level playing field".
But the former House speaker admitted he felt disadvantaged, saying the president appeared to have the backing of unions, Hollywood and "elite media".
"If you're a conservative, you must start with the assumption that you're not going to get a break from the elite media," he said.
Mr Gingrich is seen as a font of conservative policy ideas and controls a broad network of non-profit organisations and business ventures.
But he is twice divorced, and in the 1990s - while he was leading the charge to impeach President Bill Clinton in connection with his affair with a White House intern - he had an extramarital affair with the woman who became his third wife.
Socially conservative voters influential in the Republican primary race could be turned off by that past, analysts say.
Test the waters
Other likely Republican 2012 candidates include former Massachusetts Governor Mitt Romney, former Alaska Governor Sarah Palin, former Arkansas Governor Mike Huckabee, former Utah Governor and US ambassador to China Jon Huntsman, former Minnesota Governor Tim Pawlenty and real estate mogul and reality TV show star Donald Trump.
Of those, only Mr Romney and Mr Pawlenty have taken the first official step toward a candidacy, the formation of exploratory committees to test the waters and begin raising money.
The race for the Republican Party nomination has been slow to take shape this year, even though Democratic President Barack Obama is seen as vulnerable; the first ballots will be cast on 6 February in the Iowa caucus.
Of the candidates deemed most credible by the US news media, only Mr Pawlenty attended the first Republican presidential debate held last week in South Carolina.
But he is twice divorced, and in the 1990s - while he was leading the charge to impeach President Bill Clinton in connection with his affair with a White House intern - he had an extramarital affair with the woman who became his third wife.
What a hypocrite!
At least Bill Clinton hasn't been divorced twice.
How about a third time, Newt?
Mrs. Earl is a Republican (albeit one who is quite disillusioned because the leadership of her party welcomed Southern segregationist white conservative Democrats into the party without changing their views), but she will never vote for Gingrich under any circumstances. As for me, I won't be voting in the next election cycle (or at all ever again, except perhaps in local elections from time to time) because I completely gave up on politics a long time ago.
"Some cause happiness wherever they go; others, whenever they go." -- Oscar Wilde
Newt Gingrich cried like a baby because he couldn't get a window seat on the Presidential plane Air Force One.
What a fucking retard!!!
No way would I want Newt Gingrich as President!
Who wants a President who's still in diapers?
I'm fat and sassy! I love to sing & dance & stomp my feet & really rock your world!
All I want to hear from an ex-jock is "Will that be paper or plastic?" After that he can shut the fuck up!
Heah comes da judge! Heah comes da judge! Order in da court 'cuz heah comes da judge!
I'm pretty sure that the recent capture and killing of Bin Laden will do quite a lot for Obama's chances of winning the next election. I'm not too sure on how he's handling the economy at the moment, though, so who knows what may happen yet.
I think we should demand to see his birth certificate, and the long form of it at that. Come on....with a name like "Newt", he's obviously an amphibian -- and we know amphibians aren't natural-born citizens, and therefore he can't be allowed to be President!
Donald Trump says he won't run for US president in 2012
Tycoon Donald Trump says he will not run for the US presidency in 2012, declaring he is not ready to leave the private sector.
On Monday, he said he could win, but "business is my greatest passion".
In recent months, the real estate mogul and reality television star had loudly questioned whether President Barack Obama was born in the US.
The media attention that gained, and his existing fame, boosted him to the top tier of candidates.
In a statement on Monday, Mr Trump said that through his "unofficial" campaigning, he had come to realise that "running for public office cannot be done half-heartedly".
Mr Trump, who hosts the reality television programme Celebrity Apprentice, made his announcement on Monday as the NBC television network rolled out its line-up of forthcoming shows.
Prior to the announcement, NBC said it would bring back the programme with a different host if Mr Trump ran for president.
The New York businessman had been flirting with a presidential bid for months, even travelling to early primary states like New Hampshire.
Last month, Mr Trump demanded that Mr Obama release copies of his birth certificate, adding fuel to rumours among certain groups that the president was not born in the US.
The president ultimately released the certificate, and Mr Trump took credit for forcing Mr Obama's hand.
Had he run, Mr Trump would have had to make significant disclosures about his financial interests and undergo scrutiny of his business activities, and analysts had suggested that prospect could dissuade a candidacy.
And Mr Trump's tumultuous personal life - played out in past decades across the pages of New York's tabloid newspapers - his ideological inconsistency, his reputation as a showman and his lack of political experience could have proven problematic for serious-minded and doctrinaire Republican primary voters, correspondents say.
Mr Trump's news comes only days after Mike Huckabee, a Republican and former governor of the US state of Arkansas, announced he would not seek the Republican nomination for the presidency.
Former Republican House Speaker Newt Gingrich and Texas Congressman Ron Paul both announced their intention to run last week.
Other potential Republican 2012 candidates include former Massachusetts Governor Mitt Romney, former Utah Governor and US ambassador to China Jon Huntsman, and former Minnesota Governor Tim Pawlenty.
Of those, only Mr Romney and Mr Pawlenty have taken the first official step towards a candidacy, by forming exploratory committees to test the waters and begin raising money.
I see you're becoming almost as cynical as I am!!!
Aw gee! Have I been a bad influence on you?
I certainly hope so!!!
I'm fat and sassy! I love to sing & dance & stomp my feet & really rock your world!
All I want to hear from an ex-jock is "Will that be paper or plastic?" After that he can shut the fuck up!
Heah comes da judge! Heah comes da judge! Order in da court 'cuz heah comes da judge!
I'm fat and sassy! I love to sing & dance & stomp my feet & really rock your world!
