Washington: Newt Gingrich officially ended his campaign on Wednesday, and US President Barack Obama's re-election campaign released a web video of clips from the Republican primaries in which the former House speaker sharply criticized Mitt Romney - President Obama's likely opponent in November in the US presidential elections.
Facing a tight race, Obama's campaign put forward Gingrich's anti-Romney messages on issues from immigration to the presumptive nominee's tenure as a venture capitalist.
Gingrich 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 tried to stage a political comeback in this year's presidential contest, but he won primaries in only conservative South Carolina and Georgia, the state he represented for 20 years.
As he officially ended his campaign in an appearance in Arlington, Virginia, Mr Gingrich thanked a long list of supporters and said the run for the Republican nomination had been "an amazing year" for him and his wife, Callista.
"Suspending the campaign does not mean suspending citizenship," said Mr Gingrich as he read off a valedictory enumerating his long history of working for what he saw as critical issues for the United States and conservative political victories.
Looking forward to the November election, Mr Gingrich put himself behind Mitt Romney's candidacy by saying there was no choice between him and President Obama, who he called the "most radical American president in history." But there was little praise for Mr Romney's candidacy, a reflection of lingering hard feelings after the presumptive nominee crushed him and closest Republican rival Rick Santorum with scorching negative advertisements in the primaries.
The bitter primary battle gave the Obama camp plenty of material for the video of a fellow Republican lashing out at Mitt Romney.
Mr Romney, meanwhile, was kicked off his campaign in Virginia, a critical swing state that is not firmly behind either the former Massachusetts governor or President Obama, who carried it in 2008. Republican George W Bush won the state in 2000 and 2004.
At a rally in the Northern Virginia suburbs of Washington, Mr Romney spoke about the economy.
"What I would do? People ask me, 'What would you to get the economy going'? and I say, 'well look at what the president's done, and do the opposite," Mr Romney told a group gathered at a warehouse in Northern Virginia.
He was in the Washington area to raise money and hold a series of meetings at the Republican National Committee, where he's working to integrate his campaign with the national party apparatus.
After several days of campaigning marked by the anniversary of the death of Osama bin Laden, Mr Romney's campaign returned to familiar themes of the economy and jobs. He painted small businesses as heroes of the economy and said legislation President Obama signed to regulate the banking industry was hurting smaller institutions.
"They've gotten bigger; and the small community banks are the ones that have been most hurt," Mitt Romney said.
Ann Romney introduced her husband with an appeal to the women in the audience.
"We appreciate all these women being here," she said, noting that Exhibit Edge, the company where the event was held, is run by a woman. "We know what women can do ... how women actually do make the world go round."
President Barack Obama was preparing for two fundraisers Wednesday night just hours after he returned from 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 President Obama ordering a Navy SEAL raid into Pakistan that killed Al Qaeda leader Osama bin Laden.
As Barack Obama again assured Americans the Afghan war was coming to an end, he said that during his presidency "the tide has turned. We broke the Taliban's momentum. We've built strong Afghan security forces. We devastated al-Qaida's leadership, taking out over 20 of their top 30 leaders."