Lt. John Rodgers, a 20-year veteran of the sheriff's office in Clark County, where Springfield is the county seat, made the statements in several posts on Facebook, WHIO-TV reported.
"I am sorry. If you support the Democrat Party I will not help you," Rodgers reportedly wrote in one post. Another said: "The problem is that I know which of you supports the Democratic Party and I will not help you survive the end of days."
The sheriff's office said Rodgers, who has commanded the department's road patrol, would remain on duty, with a written reprimand for violating the department's social media policy.
"We've been in this battle over the last few months, with the attacks on the Haitian community and other immigrants, and we protect people's rights and we don't support the conduct to the contrary," Mike Young, the county's chief deputy, told the Springfield News-Sun. "I can't go back in time and take that post away; the lieutenant made the post and he has received consequences for that."
Former President Donald Trump, the Republican presidential nominee, and his running mate JD Vance, drew Springfield into the national spotlight with false claims - some made during a nationally televised presidential debate - that the city's Haitian immigrants were eating people's pet dogs and cats. Springfield is in southwestern Ohio between Columbus and Dayton.
Clark County Elections Director Jason Baker said Rodgers was not scheduled to be at the county elections board on Tuesday night, but that the sheriff's office is still planning to send other officers there to provide security during the election count.
"I think the public should still be safe, with the Clark County sheriff's department and the Springfield Police Department at work," he told The Associated Press. "We're all fighting for the same outcome, which is to have a peaceful day."
A sheriff's office statement said the posts do not reflect the office's mission and values.
"It is understood that while these comments are highly inappropriate, they in no means reflect the Clark County Sheriff's Office delivery of service to ALL our community," the statement said. "The community has a right to be upset over the actions of Lt. Rodgers and he, as well as the Sheriff's Office in general, will have to work even harder to replenish the trust of members of our community."
Rodgers formally responded to the reprimand, writing in a letter in his personnel file that he does not recall writing the posts or taking them down, and was alerted to them when a coworker asked if he was OK, the Springfield News-Sun reported. Rodgers wrote that he did not find them on his page when he searched for them and that the first time he saw them was during a meeting with a department official.
Rodgers said he sometimes takes a prescribed sleep aid that can cause him to send "out of character" texts, phone calls or other forms of communication as a side effect. The lieutenant said that as soon as he learned of the messages on Tuesday, he deactivated his Facebook account and stopped taking the medication, the newspaper reported.
Clark is not the only Ohio county dealing with controversial statements made by law enforcement officials on social media.
The U.S. Department of Justice's election monitoring operation is on site in Portage County, in the northeastern part of Ohio, to ensure the county complies with federal voting rights laws during early voting and on Election Day.
That's after Portage County Sheriff Bruce Zuchowski, a Republican, was accused last month of intimidating voters. Zuchowski, who is running for reelection, posted on social media that people with Kamala Harris yard signs should have their addresses written down so that immigrants can be sent to live with them if the Democrat wins the presidency.
In the wake of the comments, the Portage County Board of Elections voted to forego using sheriff's deputies for election security this year.
Asked at a news conference Monday about how the two cases might impact voters' feelings of safety, Republican Secretary of State Frank LaRose said some law enforcement officials - particularly when they're running for office - can sometimes make comments that are "ill-advised."
"But that doesn't, in any way, implicate the dedicated sworn deputies that work for them," he said. "Those are dedicated people that are first and foremost lawmen and women. They've sworn an oath to do this. They put their life on the line to do this, and I have every confidence that they take that duty very seriously."