Republican rivals Eric Greitens and Eric Schmitt each quickly claimed that Trump had endorsed them after the ex-president endorsed simply "Eric."
The Show-Me state, which once elected a dead man to the Senate, is again living up to its reputation for messy elections.
Greitens has faced accusations of abuse and blackmail but has denied any wrongdoing on his part.
The former governor is currently the front runner in the race for the GOP's senate nomination.
The former governor is holding a gun for the duration of the ad while men wear around him camouflage gear.
The Missouri GOP Senate candidate faces accusations of promoting political violence in the advertisement.
The former Missouri governor's new campaign video comes as he faces allegations of domestic abuse against his wife and child.
"His children deserve a father who will speak the truth and stand up against malicious attacks that are clearly politically motivated," wrote his campaign.
Greitens, who has recently been accused of being physically abusive to his ex-wife and children, is the leading Republican candidate in Missouri's Senate race.
The Republican former governor of Missouri was accused of domestic abuse in court documents related to a child custody dispute.
He faced the felony charge of invasion of privacy.
Greitens was accused previously of sexually assaulting and blackmailing a woman with whom he had an affair.
"I am disgusted, disheartened, and I believe Governor Greitens is unfit to lead our state," Wagner said.
The case against Greitens stems from his admission in January that he had an extramarital affair with his hairdresser.
"The serious allegations against Missouri Governor Eric Greitens are very troubling," the circuit attorney said on Thursday.
Missouri's Republican governor has apologized after a broadcast accused him of blackmail.
Stockley, a police officer, has been acquitted in St. Louis six years after he shot and killed Anthony Lamar Smith.
The police officer is being tried in the murder of Anthony Lamar Smith.
If passed, the legislation would also enable anti-abortion crisis pregnancy centers to operate without risk of political restriction.
Governor Eric Greitens has called a second extraordinary session in his first year in office to discuss stricter rules on abortion.