Republican presidential candidate Newt Gingrich is expected to suspend his campaign next week and endorse Mitt Romney, his spokesman has said.
Mr Gingrich now says he expects Mr Romney, who won five primaries on Tuesday, to be the Republican nominee.
The campaigns are said to be working out an orderly endorsement, with Mr Romney keen on Mr Gingrich's support.
He has won only two primaries - South Carolina and Georgia - since the election season began in January.
The Gingrich campaign had indicated it would reassess its future if he did not win the contest in Delaware.
Mr Gingrich will reportedly hold his last campaign event on 1 May in Washington DC.
During a campaign stop in North Carolina on Wednesday, Mr Gingrich all but conceded.
"You have to at some point be honest about what's happening in the real world as opposed to what you would like to have happened," Mr Gingrich told supporters.
He added that Mr Romney "had a very good day yesterday. You have to give him some credit."
The former House Speaker said he would continue to campaign for the next week as a "citizen", adding he would discuss economic issues, such as high unemployment.
"We are going to stay very, very active and we are working out the details of our transition," Mr Gingrich said. "But I am committed to this party. I am committed to defeating Obama."
He was expected to go ahead with several scheduled campaign stops across North Carolina.
Gingrich spokesman RC Hammond said the former House Speaker was planning an event to throw his support behind Mr Romney, after having spoken to him on Wednesday.
He told US media Mr Gingrich would suspend his campaign once an orderly process had been arranged that would maximise the benefits to the Republican party and to Mitt Romney.
"Newt is committed to helping the party stop Barack Obama's second term," Mr Hammond said. "He will do everything he can to make sure that happens."
The former House Speaker had campaigned heavily in Delaware ahead of Tuesday's primary, a state that Mr Romney all but ignored.
But Mr Gingrich still lost the state's vote by 30%.
Bob Walker, a Gingrich adviser and former US representative, said on Tuesday: "I don't think we can lose by 30 points in Delaware and feel good about it."
In December, Mr Gingrich confidently predicted he would become the Republican nominee, and for a time enjoyed high poll ratings.
Although he won his home state of Georgia and nearby South Carolina, Mr Gingrich racked up heavy losses as the primary season continued.
He had vowed to fight on, even as Rick Santorum, Mr Romney's main Republican challenger, suspended his own campaign earlier in April.
Following Tuesday's wins, the Romney campaign will begin formally integrating with the Republican National Committee.
RNC chairman Reince Priebus said on Wednesday he had directed its staff to start communicating with Romney advisers.
Former Massachusetts Governor Romney has an unassailable lead in the race for the 1,144 delegates needed to secure the Republican nomination at the party convention in August.
Texas Congressman Ron Paul is the only other remaining candidate in the race, although he cannot win.