A candidate for office in Missouri, who won his Republican primary by just 33 votes, faces federal charges for allegedly trying to plant cocaine on his opponent.

Thomas Ross, 37, recently defeated Louise Secker in the GOP contest for State House District 101, winning by narrow margins last month. 

According to an affidavit, Ross asked his campaign manager to plant a small amount of cocaine and a prescription amphetamine pill on Secker in the days leading up to the August 4 primary. 

The former campaign manager told law enforcement officers that Ross provided him with a black nylon glove that contained a small, plastic bag of white powder and a pink and white capsule. 

He said Ross told him to place it in Secker's purse or vehicle while Ross was out of state on vacation, according to a probable cause statement signed by an FBI agent.

Court records also show that the FBI gave the former campaign manager a recording device and allegedly caught Ross agreeing to the plot of planting the drugs on Secker and calling in an anonymous tip. 

Law enforcement tests later showed the substances to be cocaine and Adderall.

The FBI statement said Ross sent numerous text messages to his campaign staffer regarding 'the substance.' 

In one, Ross said he hoped 'that we could make it happen' before Secker attended a Republican women's meeting at a Joplin restaurant in June, 'which would be extreme egg on the face,' according to the FBI document.

US Attorney R Matthew Price said in a statement that voters deserve to have confidence in elections.

'Candidates are expected to conduct their campaigns with integrity, honesty, and respect for their opponents, allowing voters to make informed decisions without fear of misinformation or undue influence,' he added. 

'Our citizens deserve to know that the election process is done with transparency and fairness,' said FBI Kansas City Special Agent in Charge Chris Ormerod. 

'As this case moves through the judicial process, it's important that it proceeds fairly, impartially and in accordance with the rule of law.'

Missouri's Republican Party chairman, Peter Kinder, called on Ross to drop out of the race, describing the circumstances of his arrest as 'serious and deeply troubling.' 

'Given the seriousness of this situation, I believe the right course of action is clear. I am calling on Mr Ross to immediately withdraw his candidacy and step down as the Republican nominee for House District 161,' he said.

'The people of Southwest Missouri deserve nothing less than leadership they can trust.' 

The case is being prosecuted by US attorneys and investigated by the FBI and police in Joplin. 

When reached by The Daily Mail for comment, Secker sent a letter written by her attorney, Phillip A Glades.

'Ms Secker has been made aware that there has been an ongoing investigation into her opponent in the recent State Legislature election and that he has now been arrested,' Glades said.

'Ms Secker does not know what charges are filed or may be pending. Inasmuch as the investigation may be ongoing, it would be improper for her to make any comment at this time.'  

Ross did not respond to a Thursday message seeking comment about the charge, which was filed Wednesday. 

The federal public defender's office assigned to his case didn't immediately reply to a message asking how Ross plans to plead. 

The Daily Mail has reached out to both Ross' campaign and Secker for comment.