Mr Gingrich represented a Georgia constituency in Congress for 20 years Former Republican House Speaker Newt Gingrich is expected on Wednesday to announce a 2012 run for the presidency.
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.
On his Twitter feed, Mr Gingrich, 67, advised supporters to watch conservative television personality Sean Hannity’s programme on Fox News on Wednesday evening.
“I will be on to talk about my run for president of the United States,” he wrote.
His entrance into the race has been widely anticipated.
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.
Other likely 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.
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