It’s led by Mark Burton, who was Whitmer’s chief of staff during her tenure in the state Senate.

Burton said the group’s top issues include skills training, K-12 education and access to affordable health care.

Build a Better Michigan plans its ad buy over a five-week period, starting with the Detroit, Flint and Grand Rapids markets, Burton said. Nowhere in the initial 30-second spot does the group explicitly encourage viewers to vote for Whitmer in the Aug. 7 primary.

Why does the ad tiptoe around endorsing Whitmer?

In Michigan, a federal 527 organization is not required to report finances to the state if their ads avoid telling voters who or what to vote for, said Fred Woodhams, a spokesman for the Michigan Secretary of State.

Craig Mauger, executive director of the Michigan Campaign Finance Network, a nonpartisan nonprofit, said political organizations that fall outside of Michigan’s campaign finance laws — like 527 organizations — can coordinate with candidates if they don’t directly advocate for or oppose their candidacy.

That could explain why Whitmer is appearing in Build a Better Michigan’s ad.

Federal requirements are different: 527 groups have to report details of their donors and spending to the IRS, though they’re only required to list names and addresses of donors who give at least $200 in a calendar year.

Burton told Truth Squad the organization will make its first quarterly report to the IRS, covering the three-month period from April 1 to June 30, by July 15.

Adam Joseph, El-Sayed’s campaign spokesman, said the campaign has not yet seen details of Build a Better Michigan’s finances.

But he contends the organization was created to promote Whitmer as a candidate. (A claim also made by the Michigan Republican Party, which filed a complaint Wednesday with state election officials.) And Joseph notes that a 527 allows candidates like Whitmer to benefit from unlimited amounts from corporations that wouldn’t otherwise be allowed to donate directly to a candidate’s campaign, while also shielding from public view the original source of some contributions.

Corporations can’t donate directly to candidates for office in Michigan, though they can give to super PACs supporting a candidate. State campaign finance law limits donors to individual candidates running for governor to a maximum of $6,800 for each election cycle.

“Campaigns like Sen. Whitmer’s use 527s for two reasons: first, to take unlimited amounts of corporate money, and second, to launder donations through other PACs, dark money accounts, and other sources,” Joseph told Truth Squad in an email. “And because we don’t know where any of the $1.8 (million) ‘Build a Better Michigan’ is spending to advertise for Whitmer is coming from — it is dark money.

“We have invited Sen. Whitmer to disclose her contributions — to bring light to a dark money situation — but she seems less interested in transparency or accountability than in playing by Republican rules and letting corporations buy her campaign.”

Whitmer’s campaign notes, correctly, that it is a separate legal entity than Build a Better Michigan. The campaign also takes the position that Whitmer was invited to appear in its ad to promote various issues, not her candidacy.

“Neither she nor anyone on the Whitmer campaign has any authority to direct the activities of Build a Better Michigan,” campaign spokesman Zack Pohl said in an emailed statement. “Gretchen believes every outside group and independent PAC should fully comply with campaign finance and IRS disclosure laws.”

Burton declined to voluntarily disclose the group’s donors ahead of the July filing deadline.

“Our intent has always been, and will continue to be, to follow the letter of the law regarding both contributions and expenditures,” Burton said.

August 2, 2018 update: The filing deadline has passed, the Truth Squad re-examines this claim

“We haven’t begun filling out a report of any kind, but it’s a lot of organizations and some individuals from across the state who care about the particular issues that we’re talking about in this ad,” he said. “Gretchen Whitmer obviously is concerned about similar issues, so she makes a great spokesperson in that regard for us. But I don’t want to name any names right now.”

Michigan and national campaign finance experts told Truth Squad that political groups such as 527 organizations are not inherently dark-money organizations. As noted, they are required to report their contributions and spending. But there are ways these groups can be used to funnel dark contributions.

One example is nonprofit social welfare groups, such as civic groups organized under Section 501(c)4 of the Internal Revenue Code, said Pete Quist, research director for the Helena, Mont.-based National Institute on Money in Politics. Because the IRS doesn’t recognize social welfare groups as a political organization, they don’t have to publicly disclose their donors.

Yet 501(c)4 organizations can get involved in politics, usually through ad campaigns, and are unlimited in both who can give to them, and how much, he said.

If a 527 political organization accepts money from a 501(c)4 nonprofit that doesn’t have to disclose its donors, Quist said, “the trail pretty much runs cold from there.” The civic group will be listed as a donor to the 527, but that doesn’t tell the public much about who is funding that civic group.

Quist said El-Sayed’s statement that Build a Better Michigan is a vessel for dark money “may not be technically accurate” because it hasn’t yet disclosed its donor list. It’s simply too early to tell.

But, Quist added, “the point is well taken. Because it is a 527 organization, it will have to disclose where it’s getting its money. And until it does that, we don’t know if it’s taking its money from dark-money groups.”