In the months after Jesse Mallen’s sister died in a highway crash, looking at photos of her brought him comfort. Then he saw her face in a political attack ad. The ad, which aired across Ohio this month, shows Mr. Mallen’s sister, Lynnea Soposki, along with her husband, Luke, and their 1-year-old son, Logan.

In April, all three family members were killed when a semi truck crashed into their pickup truck on a highway north of Columbus, causing a nine-car pileup and setting their vehicle on fire. The driver, who was charged with multiple felonies, has been accused of fraudulently obtaining U.S. citizenship and Ohio drivers licenses. Titled “Dangerous for Ohio,” the ad was paid for by the National Republican Senatorial Committee and authorized by the campaign of Senator Jon Husted, who is running against former Senator Sherrod Brown, a Democrat.

Shortly after the crash, the Ohio Department of Public Safety issued a news release stating the driver entered the United States in the 1990s and “subsequently used multiple names and dates of birth to obtain state and federal identification.” The state said it was turning its investigation over to Immigration and Customs Enforcement. But the driver, Modou Ngom, has not been charged with any immigration-related crimes. His lawyer, who declined to comment on Wednesday, has said in a court motion that the state’s statements violated Mr. Ngom’s right to a fair trial.

In a statement on Wednesday afternoon, the Department of Homeland Security said Mr. Ngom was naturalized as a citizen in 2015, but did not answer a series of questions about the state’s fraud allegations. Mr. Mallen, 40, said in an interview that he privately reached out to the Husted campaign through email and certified mail last week, imploring it to stop running the ad. “What we all want is to be able to grieve in peace and privacy, and for our family to not be used in such a classless way by a politician, especially without being consulted,” Mr. Mallen said. “We certainly would not have said yes, but quite frankly, I think they knew that.” After a week of silence from the campaign, Mr. Mallen said, his family felt they had no choice but to go public. Though he has supported Democrats in the past, he said the decision was not based on personal politics, but on his certainty that his sister, who was a veterinarian in the Columbus area, would not want to appear in a political ad for any party. Mr. Mallen said his family had not been in contact with the Brown campaign. On Tuesday, Mr. Mallen began posting about the ad on Facebook and Reddit, writing, “Our grief is not raw material for a campaign.” By then, the spot had been running for at least 16 days, and it had cost Republicans an estimated $1 million, according to Ad Impact, a group that tracks political advertising.

Though it appears that the ad has been replaced by a new one attacking Mr. Brown, a clip of “Dangerous for Ohio” remains on You Tube, where it has more than five million views. Nick Puglia, a spokesman for the N. R.

S. C., said in a statement that Mr. Brown had “backed open border policies that cost Ohioans their lives, without ever apologizing,” adding, “Our ad campaigns will continue to hold Sherrod Brown accountable.” Mr. Husted’s campaign declined to comment. Mr. Brown’s campaign also declined to comment, but pointed to an analysis by the group Fact Check.org, which states that there is no evidence linking Mr. Brown’s votes and the crash.