Washington: With Newt Gingrich officially ending his campaign on Wednesday, only Texas Representative Ron Paul remained as a nominal challenger to Mitt Romney, who has all but locked up the Republican nomination to challenge President Barack Obama in November.
The libertarian Paul, who has conducted a minimalist campaign and has the support of a small but determined following, appears ready to stubbornly stay in the race until the party`s national convention in August.
Gingrich, the former speaker of the House of Representatives, led the Republicans out of 40 years of minority status in the lower house of Congress in 1994 but later resigned under an ethics cloud.
He was trying to stage a political comeback in this year`s primary contests, but he won primaries in only conservative South Carolina and Georgia, the state he represented for 20 years.
As he prepared to officially end his campaign, Gingrich thanked supporters in a video message posted on his website, saying their help was vital.
His campaign has reported being more than $4 million in debt, despite millions pumped by a gambling casino owner into an allied super political action committee.
Gingrich pledged to work hard to prevent the "genuine disaster" he says would result from re-electing Obama, but he did not mention Romney, who crushed him and closest Republican rival Rick Santorum with scorching negative advertisements in the primary contests.
Those state elections and caucuses do not end until late June, but Romney was expected to have rolled up the 1,144 delegates needed for the nomination by late this month.
As Gingrich prepared to withdraw, Obama was making an unannounced visit to Afghanistan to sign a pact that outlines a 10-year US military and financial commitment to the battle-scarred nation once foreign forces turn security over to the Afghan army at the end of 2014.
As part of the trip, Obama addressed the US people on national television from the US military headquarters at the Bagram air base north of the Kabul.
The journey coincided with the anniversary of Obama ordering a Navy SEAL raid into Pakistan that killed al-Qaeda leader Osama bin Laden.