Democratic presidential candidate Bernie Sanders urged a crowd in Phoenix to vote in Arizona's primary after losing to Hillary Clinton in Florida, North Carolina and Ohio on Mar. 15. (Reuters)

Democratic presidential candidate Bernie Sanders urged a crowd in Phoenix to vote in Arizona's primary after losing to Hillary Clinton in Florida, North Carolina and Ohio on Mar. 15. (Reuters)

Democratic front-runner Hillary Clinton appeared to have won the Missouri primary by a slim margin, but that race remained in limbo Wednesday pending tallies of additional ballots and word on whether rival Bernie Sanders would seek a recount.

The delay postponed a definitive answer to whether Clinton had made a clean sweep of five big primaries on Tuesday night. Regardless, her dominant performance pushed her closer to the Democratic presidential nomination even as both campaigns predicted that Sanders could go on something of a winning streak over the coming month.

On Tuesday, Clinton won big in Florida, North Carolina and Ohio, while claiming a narrower victory in Illinois. In Missouri, with 100 percent of precincts reporting, Clinton was ahead 310,602 to 309,071. Those figures did not include an undetermined number of provisional, military and overseas ballots that could affect the outcome.

With a difference of less than 1 percent, Sanders has the right to request a recount four weeks from now, once the results are certified, election officials said. That probably would mean a winner would not be declared until May.

Jeff Weaver, Sanders’s campaign manager, said the campaign, still looking at the final numbers, has not made a decision on whether to request a recount. Because delegates are awarded proportionally, it’s unclear how much a small change in the vote totals would matter, he said.

“If it’s not going to make a material difference in the delegate count, we’re not going to put people through it,” he said.

Clinton’s victories on Tuesday put her more than 300 delegates ahead of Sanders, not including super­delegates. The former secretary of state also enjoys a considerable lead among that group, made up of elected officials and party leaders who are not bound by the preference of voters.

Sanders ended Tuesday further behind in the delegate count — and needing to win a slew of upcoming states by improbably large margins.

Both campaigns said Wednesday that they expect Sanders to win some states in the coming weeks, starting Tuesday, when Arizona, Idaho and Utah hold contests. Primaries and caucuses then follow in Alaska, Hawaii, Washington state and Wisconsin.

In a fundraising appeal to supporters Wednesday, the senator from Vermont asserted that he has “an extremely good chance to win nearly every state that votes in the next month.”

“Starting today, the map now shifts dramatically in our favor,” Sanders said.

Clinton’s campaign manager, Robby Mook, also acknowledged Wednesday that Sanders could have a winning streak in states where the demographics are more favorable to him.

Democratic front-runner Hillary Clinton and her rival, Bernie Sanders, spoke about the challenges going forward after primary voters took to the polls in five states on March 15. (Sarah Parnass/The Washington Post)

“Looking ahead to the rest of March, Sen. Sanders is poised to have a stretch of very favorable states vote, including five caucuses next week, which he is likely to win, and the primary in Arizona, in which he has invested more than $1.5 million in ads,” Mook wrote in a memo to supporters and the news media.

Mook and the Sanders campaign diverged on what impact such a stretch would have on the direction of the race.

Mook wrote that “our pledged delegate lead is so significant that even a string of victories by Sen. Sanders over the next few weeks would have little impact.”

Weaver argued that the coming contests could be the start of a big comeback for his candidate.

He said that between now and the convention in July, Sanders would “steadily, consistently and ultimately successfully erode [Clinton’s] lead in pledged delegates.”

Weaver said in an interview that the second half of the calendar is far more favorable to Sanders than the first.

“This is really like halftime in a football game, and obviously she’s run up the score somewhat,” Weaver said.

He stressed that fewer than half of the Democratic delegates have been picked to this point and said he sees opportunities for Sanders to win in “showdown” states including Wisconsin, New York and California.

He said the campaign has plotted out a scenario in which Sanders catches Clinton in pledged delegates after California, which votes in June. He would not share his numbers.

Even if Sanders were to mount a comeback, he faces another large hurdle: flipping super­delegates.

The superdelegates account for nearly a third of the number of delegates that a candidate needs to secure the nomination. And so far, Clinton has a super­size advantage.

Before Tuesday, she led 467 to 26, according to a count by the Associated Press.

Sanders and his aides argue that many could change their allegiances if he starts winning more pledged delegates — and more states. The thinking is that Democratic leaders would not want to have a nominee chosen by party insiders rather than the voters.

There are also more than 200 Democratic superdelegates who have not yet announced a preferred candidate.

Sanders spent Wednesday in Arizona huddling with aides and did not make any public appearances. He has a rally planned Thursday in Flagstaff.

“We’re in the locker room at halftime,” Weaver said.

Clinton also had no public events Wednesday and is planning to raise money for the rest of the week, aides said.

Gearan reported from Washington.