Andrew Gillum's campaign for governor hasn't been the luckiest.

Just a few months into the Tallahassee mayor's run, FBI agents delivered a subpoena to his city hall in June 2017, requesting thousands of pages of records from key players in city government. The investigation has since dogged Gillum's campaign, with new developments dripping out with unpredictable frequency.

The FBI is usually tight-lipped about pending matters. Although Gillum has not been named in any subpoenas, it's likely that Democratic primary voters won't know the case's outcome before they head to the polls Aug. 28.

Here are three questions about the FBI's investigation into Tallahassee's city government and how it relates to Florida's governor's race.

1. What is Gillum's connection to the case?

Starting in 2015, FBI agents came to town posing as businessmen considering investments in the city of Tallahassee. The three men, who reportedly identified themselves as Mike Sweets, Mike Miller and Brian Butler, spent months cozying up to city officials and people close to them. The FBI investigation based in part on their undercover work has yielded several rounds of subpoenas — but no charges yet.

A slew of Tallahassee officials and insiders have been named in those subpoenas over the past year. According to those documents, which you can read here, here and here, the part of the investigation that could be most relevant to Gillum centers around the city's community redevelopment agency, which steers private and public money to revitalization and infrastructure projects.

One of the officials in the crosshairs of the FBI, lobbyist Adam Corey, was a longtime Gillum friend and ally until Gillum cut ties with him last year the Tallahassee Democrat has reported.

In 2013, the community redevelopment agency voted to give $1.3 million in taxpayer money to help a Corey-associated restaurant project, the Edison. Gillum voted with the rest of his fellow city commissioners — who sit on the CRA — to fund of project. At the time, Gillum's vote raised eyebrows because of his close association with Corey. One year later, Corey served as the treasurer of Gillum's mayoral campaign.

According to the Democrat, Corey became close with Miller, reportedly introducing Gillum to the undercover agent sometime in 2016. One of the reported meetings between Corey, Gillum and Miller at the Edison in May of that year became a point of controversy when the Democrat reported that Corey scheduled the meeting while on vacation with Gillum and another city lobbyist in Costa Rica. Gillum has maintained he did not discuss business in Costa Rica; the trip was merely a vacation with longtime friends, he has said. Gillum also said he paid for his entire portion of the getaway.

Gillum also joined Corey and Miller in New York in August 2016 at the end of a business trip Gillum took in his capacity with the liberal People for the American Way Foundation. In an email inviting Gillum to meet up in New York, Corey noted that Miller had arranged hotel rooms, an outing to a Mets game and a boat trip to the Statue of Liberty, the Democrat reported. Gillum's group may also have attended a performance of the hit musical Hamilton. (Tallahassee Reports first reported Gillum's New York Trip.)

Gillum didn't confirm to the Democrat whether he attended the baseball game or the show, but there are pictures of the mayor and Corey on the boat ride. Gillum has said he didn't allow Miller to pay for any part of his trip to New York, and his office calendar from that time reportedly said he stayed at a different hotel.

So how do all of these pieces fit together?  Miller, the undercover agent, wanted the city to expand the jurisdiction of the community redevelopment agency to include a parcel of land Miller said he would develop. He solicited Corey's help to achieve that goal, and in 2016, the CRA — of which Gillum is the chair — voted unanimously to expand the jurisdiction. The good news for Gillum? The mayor wasn't present for that vote.

2. What don't we know?

The most important thing voters don't know for certain is the extent of Gillum's exposure in the investigation. There's currently no indication that Gillum is in any way directly implicated — and the mayor for months has said the FBI told him in a meeting with no lawyer present that he's not the focus of the investigation.

Corey appears to be Gillum's closest link to the case, but documents indicate the FBI inquiry is wide in scope. Especially before charges are filed, it can be difficult to see a case's contours.

Even if Gillum is not implicated in the government's case, it would be unusual for the FBI to officially clear him, said Tallahassee attorney Steven Andrews, who's previously worked with subjects of FBI investigations.

Another thing we don't know: Whether the FBI will continue to make public progress in the investigation before the August gubernatorial primary. An unofficial, but often-cited Department of Justice regulation states that officials are not to discuss or act on investigations within 60 days of an election. (The DOJ, which oversees the FBI, did not respond to a question about whether that is official policy.)

The Democrat reported in July that there are signs the case could be entering the charging phase. Certain officials who may be implicated in the investigation have been seen at the federal courthouse in Tallahassee in recent days.

On the other hand, Andrews said he's seen an FBI investigation drag on for as long as seven years.

3. How has the case affected the governor's race?

It's difficult to isolate the impact of individual factors on something as fluid as a political campaign. But Gillum's own team admits the investigation hasn't exactly been a boon to the candidate — particularly when it comes to fundraising.

"It hasn't been helpful," said Geoff Burgan, a Gillum campaign spokesman. "Any time you're speaking with donors or folks like that about something that's not related to the policies you want to implement or your vision for the state, it's not going to be an optimal conversation."

Still, Burgan noted, voters rarely mention the investigation on the campaign trail.

Gillum's Democratic opponents also haven't seized on the issue. A Florida voter would be hard-pressed to find a negative television advertisement about Gillum. And when Chris King, one of Gillum's opponents, was asked about the investigation in a gubernatorial debate in June, King defended Gillum.

Aubrey Jewett, a political science professor at the University of Central Florida, said there are a number of reasons for Democrats' reluctance to weigh in. The case is still murky and Gillum hasn't been implicated in any wrongdoing, so Gillum's opponents would be going out on a limb somewhat to knock him for the investigation, Jewett said.

Gillum also hasn't polled consistently well enough to warrant attacks from his Democratic opponents, Jewett noted.

But if Gillum were to secure the nomination, it's extremely unlikely that his Republican general election opponent would hold his fire, said Florida State University political science professor Carol Weissert in an email to the Tampa Bay Times.

"Floridians—or really any voters—don't want to put a 'tainted' candidate in office," Weissert wrote. "Gillum isn't well-known among voters which means he doesn't have a reservoir of goodwill to draw down on against tough corruption allegations."