Labor Day weekend arrives with the United Auto Workers facing one of the darkest periods in its history, engulfed in an ever-growing scandal that now touches the very top ranks of the union’s leadership.

Federal agents investigating corruption within the U.S. auto industry carried out raids this week on homes of UAW President Gary Jones and former President Dennis Williams, suggesting the two are targets of the probe into bribery and kickbacks aimed at influencing labor contract negotiations.

No arrests were made, and Jones is said to be cooperating with the FBI.

Already, the feds have brought charges against nine people connected to the UAW and Fiat Chrysler Automobiles. Wednesday, Michael Grimes, a former UAW official with close ties to Vice President Cindy Estrada of the union’s GM team, was charged with taking bribes in the form of cash, checks and other valuables.

The expanding scope of the investigation and the implication of Jones raises the possibility that a union that has always prided itself on being squeaky clean could be hit with racketeering charges, which could ultimately lead to government oversight of the union.

Jones deserves a strong presumption of innocence, as does Williams. The FBI often conducts raids that produce no criminal charges, and often are targeting someone other than the homeowner. And if they are charged, their guilt or innocence will be decided by a jury, not by public opinion.

Still, both supervised those who have been indicted, and at the very least they are guilty of keeping less than stellar oversight of their staff. Those scooped up in the probe include direct reporters to the two presidents, including Norwood Jewell, a former vice president of the union.

Jones and Williams are also responsible for at least some of the free-spending the FBI is also focused on, including a cottage for Williams at the UAW resort on Black Lake and conferences at luxury hotels.

Their fitness for leadership is very much in doubt. Their laxness has already cost the UAW a seat on the GM board that was held by former UAW Vice President Joe Ashton, limiting the ability of the union to protect its members from the inside of the company, a rare opportunity for an American labor organization.

Meanwhile, the UAW is in the final stages of contract negotiations with the Detroit Three. The current contract covering 1.4 million members expires Sept. 15.

After a decade-long stretch that saw record profits pouring into automaker coffers, autoworkers are expecting a significant bump in their financial package. Meanwhile, the companies are seeing economic red flags ahead, largely because of uncertainty about trade policies, and are reluctant to commit to significantly higher labor costs.

The complexity of these talks demands capable and uncompromised leaders on both sides of the table.

Jones is leading the bargaining for the UAW. His credibility as an honest negotiator is gone, thanks to this week’s raids. Members can’t have confidence that Jones is acting in their best interests, or that any contract proposal he brings to them is untainted by the gifts, favors and cash that have flowed to UAW officials for years.

Jones should step aside from both the bargaining and the leadership of the union while the criminal case is unfolding.

Certainly, the timing couldn’t be worse, with the talks reaching their closing stage. But UAW members, who could be asked to go on strike if a deal is not struck, must have full faith in the integrity of their negotiating team.

They also must be certain that Jones, who must sign off on contract details, can devote his full attention to bargaining and other union business. That will be challenging if he ends up having to fight criminal charges himself.

The FBI contends the bribes and kickbacks influenced the union’s 2015 contract negotiations with Fiat Chrysler and General Motors. Those payouts allegedly continued after that pact was signed.

This time, union members must have certainty that everyone who is seated at the table is acting only in their interests. They can’t be sure of that with Gary Jones.

The UAW president should be replaced in the talks and at Solidarity House by a UAW official who is not implicated in the federal probe. That’s a shrinking circle, but it is essential that a stand-in for Jones be named until the depth of his involvement, if any, in the corruption is known.