WASHINGTON - New Jersey Governor Chris Christie and former business executive Carly Fiorina ended their presidential campaigns on Wednesday, narrowing the field challenging front-runner Donald Trump in the race for the 2016 Republican nomination.

Christie, 53, said in a Facebook post he was leaving the race "without an ounce of regret," a day after the combative Republican's sixth-place finish in the New Hampshire primary raised doubts about his viability as a candidate.

Fiorina, 61, a former Hewlett-Packard chief executive, said in a Facebook post she would suspend her campaign. The only woman in the Republican field placed seventh in New Hampshire, one of a series of state-by-state nominating contests for the Nov. 8 election to succeed Democratic President Barack Obama.

Trump's remaining opponents, most of them mainstream Republicans, will likely benefit from their departures, which leave seven Republicans from a field that once had 17 candidates.

Trump won the New Hampshire Republican primary by almost 20 points. The fifth-place finish of U.S. Senator Marco Rubio of Florida, who had hoped to emerge as Trump's main rival after a surprise third-place showing in Iowa last week, leaves Trump without a clear challenger among the so-called establishment candidates.

On the Democratic side, U.S. Senator Bernie Sanders of Vermont, a democratic socialist, easily defeated former Secretary of State Hillary Clinton in the New Hampshire primary.

The victories in both parties by candidates considered outsiders, testified to the sizable share of American voters upset over the slow economic recovery, immigration and America's place in the world and who are willing to shake up Washington.

Trump, 69, a billionaire businessman, has a double-digit lead over conservative Senator Ted Cruz of Texas in opinion polls for the next Republican contest, the South Carolina primary on Feb. 20, according to a Real Clear Politics average of opinion polls.

Christie poured much of his campaign's resources into New Hampshire and had considered a good showing there critical. He won only about 7 percent of votes on Tuesday, despite a pugnacious performance at a Republican debate last weekend.

"Christie needed to drop out. In short, he does not have the money or organization to be viable in South Carolina and beyond," said Monmouth University pollster Patrick Murray.

"Christie was certainly hurt by Trump stealing his 'telling it like it is thunder,' but Christie was also out-organized in the ultimate retail politics state," Murray said.

SANDERS COURTS AFRICAN-AMERICANS

Trump's victory in New Hampshire showed pundits were wrong to think he would quickly self-destruct based on his penchant for insults and imprecise plans for the presidency. He had lost last week to Cruz in the first nominating contest, the Iowa caucuses.

Ohio's Republican governor, John Kasich, finished second in New Hampshire, followed by Cruz, former Florida Governor Jeb Bush and Rubio.

The odds of Trump winning the White House, once seen as an extremely long shot, improved significantly after his victory in New Hampshire, online betting site Ladbrokes PLC said.

Trump is now at 9/2, compared with 7/1 last week, meaning his chances of victory in November are now 18 percent. Clinton still had the best odds of becoming president at 50/50, Ladbrokes said.

On the Democratic side, Sanders, 74, courted the African-American vote on Wednesday, having breakfast with civil rights leader the Rev. Al Sharpton at a restaurant in New York City's Harlem neighborhood. Clinton, 68, currently has strong support from black voters, who will be crucial in the Democratic primary in South Carolina on Feb. 27.

Sharpton and Obama met at the same restaurant during Obama's successful 2008 presidential campaign - a piece of symbolism for Sanders as he tries to expand his appeal beyond liberals in the U.S. Northeast.

"My concern is that in January of next year for the first time in American history, a black family will be moving out of the White House," Sharpton, a Baptist minister and television talk-show host, told reporters afterward.

"I do not want black concerns to be moved out with them. We must be front and center and not marginalized. And Senator Sanders coming here this morning further makes it clear that we will not be ignored," he said.

Sharpton discussed a spate of police shootings of black males and other issues with the senator. Sharpton said he would not endorse a candidate until he met with Clinton.

The Congressional Black Caucus will endorse Clinton on Thursday and its members will be active in supporting her campaign, the Washington Post reported, citing U.S. Democratic Representative Gregory Meeks of New York, chairman of CBC's political action committee.

Clinton has a long history of support for civil rights. She also has benefited from husband Bill Clinton's popularity in the black community during his presidency, although that became strained during her fierce 2008 primary battle with Obama.

Clinton's campaign, highlighting her popularity among black and Latino voters, said in a statement on Tuesday: "It will be very difficult, if not impossible, for a Democrat to win the nomination without strong levels of support among African-American and Hispanic voters."