Donald Trump at a rally in Iowa. Steve Pope/Getty Images Donald Trump appears to be making up ground in Ohio, a key battleground state whose support the Republican presidential nominee most likely needs to win the presidency.

A poll released by Bloomberg Politics on Wednesday showed Trump with a 5-point lead over his rival Hillary Clinton in the Buckeye State, a significant improvement from polls in the state conducted last month.

Among the 802 likely Ohio voters surveyed, 48% said they supported Trump, while 43% they would vote for Clinton. Nine percent were undecided.

Conducted from Friday to Monday, the poll came amid a rocky weekend for Clinton, as the Democratic presidential nominee abruptly left a 9/11 memorial service on Sunday after overheating because of undisclosed pneumonia and on Saturday was forced to address a statement saying half of Trump supporters fell into a "basket of deplorables."

Pollster J. Ann Selzer predicted that Trump's support may lie in the fact that more Republican voters than Democratic voters at the time were planning on turning.

"It is very difficult to say today who will and who will not show up to vote on Election Day," Selzer said. "Our poll suggests more Republicans than Democrats would do that in an Ohio election held today, as they did in 2004 when George W. Bush carried the state by a narrow margin. In 2012, more Democrats showed up."

Polls conducted in the past several weeks have suggested the race may be tightening in Ohio.

While a CBS/YouGov state poll released last week found Clinton to have a 7-point lead, other surveys released by Quinnipiac University and Emerson College found the candidates in a virtual dead heat.

Many political observers agree that Ohio is most likely key to a Trump victory in November.

While the real-estate mogul's massive unpopularity among minority voters makes victory difficult for him in battleground states states like Florida, he has repeatedly claimed that his popularity among some white working-class voters could help him cut a swath through Rust Belt states like Ohio, Iowa, and possibly Wisconsin.

Privately, some people close to the Clinton campaign note that the campaign has worked hard to establish a significant ground game in Ohio in preparation for a close race. Clinton will have 54 campaign offices in the state by the end of this week, while as of last month Trump had less than 20.