ARLINGTON, Va. – Even as he finally acknowledged the end of his presidential ambitions, Newt Gingrich was still thinking big.

An American moon colony, major investments in brain science research, defending against an electromagnetic pulse attack, even fixing a dysfunctional Congress will be part of the Gingrich agenda as a “citizen” rather than a presidential candidate. The former U.S. House Speaker from Georgia officially suspended his campaign Wednesday afternoon, long after realistic chances of victory had passed though Gingrich continued to push transformational plans for the country and searing attacks against all-but-certain Republican nominee Mitt Romney.

President Barack Obama's campaign put out a web video Wednesday to highlight Gingrich’s most aggressive hits on Romney, including calling him a liar on CBS’ Face the Nation. Gingrich characterized Romney as the lesser of two evils.

“Is Mitt Romney conservative enough?” Gingrich said he is often asked. “My answer is simple: Compared to Barack Obama? This is not a choice between Mitt Romney and Ronald Reagan. This is a choice between Mitt Romney and the most radical leftist president in American history.”

Gingrich spokesman R.C. Hammond said a full-fledged Romney endorsement would be forthcoming. Gingrich pledged to continue traveling in support of Republican candidates, though he is likely to take some time off. Hammond said Gingrich has been limping since August and will see a doctor to check on his Achilles tendon.

The man known best for big ideas vowed Wednesday to keep at them, even the ones that did not help his presidential campaign. When Gingrich declared on Florida’s Space Coast in January that he wanted to build a U.S. colony on the moon by the end of his second term, it was widely mocked, but Gingrich did not give up the plan. He said his wife, Callista, a constant presence at his side and major influence on the campaign, reminded him repeatedly that “the moon colony was probably not my most clever comment in this campaign.”

But Gingrich said revitalizing NASA remains a crucial project for the nation.

“This is not a trivial area,” he said. “It’s a fundamental question of whether we’re still a country that dreams and goes out to pursue adventure.”

Gingrich did not take questions from a media throng bigger than he had seen in months after delivering a 20-minute speech in a hotel ballroom a few miles from his home in the affluent suburb of McLean, Va.

Gingrich constantly played up his Georgia ties, making his first speech as a candidate to the state GOP in Macon. He officially housed his campaign in Buckhead, though the nerve center was in Northern Virginia – where Gingrich spent the rare time he was not politicking across the country.

Gingrich persisted through myriad highs and lows and outlasted nearly all his Republican rivals. He was left for dead in June when most of his staff quit, led in national polls and declared himself the likely nominee in December but ultimately could not overcome a relentless barrage of negative advertising and his own inconsistencies as a candidate.

His fiery populism and strong debate performances brought him victory in the South Carolina primary, making Gingrich the first Republican to win there and lose the nomination since the state's primary was established in 1980.

“This will make me feel slightly guilty every time I go through South Carolina,” Gingrich said.

Heavy advertising from a Romney-allied Super PAC and a couple of limp debate performances felled Gingrich in Florida and he never recovered, though he managed to win the Georgia primary on Super Tuesday – a triumph overshadowed by his losses elsewhere.

Among Gingrich’s many thank-yous Wednesday were Gov. Nathan Deal and Georgia legislators in the statehouse and Congress who backed him. Gingrich noted that he won 156 of 159 counties in his old home state and carried Carroll County, the base from which he launched his first congressional campaigns in the 1970s, with 60 percent of the vote.

“It was nice to feel we had a very strong base of support from the people who knew us best,” he said.

A pro-Gingrich Super PAC, Winning Our Future, helped sustain his bid with a media campaign funded almost entirely by the family of Las Vegas casino mogul Sheldon Adelson. Gingrich, noting their shared affinity for Israel, singled out the Adelson family for thanks, noting that they “singlehandedly came pretty close to matching Romney’s Super PAC and I’m very, very grateful to them.”

Winning Our Future still has about $5 million, according to president Becky Burkett, which she said will be used to support conservative causes such as balancing the budget, helping Romney and influencing state and local races on behalf of conservatives.  Burkett said the group will no longer take its cues from Gingrich.

“We will support the Republican nominee, and of course it appears that is Mitt Romney  ..., but there are other issues on the conservative side that we want to support as well and that may not all fit into one platform,” Burkett said.

Gingrich ended his campaign surrounded by family, including grandchildren Maggie and Robert, whom Gingrich briefly choked up when describing as “the two best debate coaches.” While devoting most of his time to the big ideas shaping the future, Gingrich reminisced about a captivating year that he often described as a roller coaster.

“I could never have predicted either the low points or the high points,” Gingrich said. “It was all sort of amazing and astonishing.”