In one of his last question-and-answer sessions before joining the national ticket, Minnesota Gov. Tim Walz was officially talking about flooding, but as was the custom back then, he took questions that were off the topic of the day.

Provided he had time in his schedule, it was the governor's general practice to entertain off-topic queries for at least a few minutes after he'd finished talking about the matter at hand. These opportunities were valuable, and reporters would often ask the governor's staff in advance if Walz would allow off-topic inquiries. Generally, he did.

Walz would answer with varying degrees of detail and enthusiasm, depending on the subject. The governor handled such sessions in a calm, polite fashion. He rarely seemed annoyed or angered.

The off-topic sessions might last a few minutes or a half hour — until a member of the governor's staff called out, "last question."

The opportunities for wide-ranging discussions with Walz evaporated when he became the No. 2 on the national ticket. In one of Walz's last news conferences before he became the vice presidential candidate, he was asked about President Joe Biden's debate against former President Donald Trump.

Walz defended Biden's acuity, saying the president was engaged and had called to check on how Minnesota was coping with the flooding. The governor also mentioned that debates are difficult and that he's not a fan of doing them himself.

Just over two months later, on Tuesday night, Walz will appear on the biggest platform of his career when he debates Sen. JD Vance, a skilled communicator and Yale Law School graduate who wrote a best-selling memoir, "Hillbilly Elegy."

Behind the scenes, Transportation Secretary Pete Buttigieg has been the governor's sparring partner in debate prep. Republican House Majority Whip Tom Emmer, who is seeking re-election to Minnesota's Sixth Congressional District, has been helping Vance prepare by playing the role of Walz.

Abou Amara, a consumer protection lawyer and former DFL legislative staffer, said Walz has been politically successful in Minnesota by being himself: happy, gregarious and off-the-cuff. But that approach doesn't make sense in a national campaign. "Message discipline is important when you're speaking to 300 million people," Amara said.

He likened it to speed dating, where the Harris-Walz ticket is trying to present itself to voters unfamiliar with them. That means repeating a succinct message while limiting unscripted interviews that can lead to missteps.

State GOP Chairman David Hann described Walz as having an erratic style that is being held in check. The Democrats' plan is to say "as little as possible about anything substantive except to say that Trump is the devil. They don't want to say why they're doing what they're going to do," Hann said.

The Walz camp deferred to state DFL Chairman Ken Martin, who countered that Walz is speaking directly to voters across the country. "JD Vance, in every uncomfortable appearance, continues to remind the American people why they're ready to turn the page on Trump's dark and dangerous agenda," Martin said.

Steven Schier, political science professor emeritus at Carleton College, said, "The more you're exposed, the more there's the possibility of gaffes. That calculation lies behind everything they're doing."

When Vice President Kamala Harris became the candidate, there was a "huge rush of positive publicity and they plan to ride that to Election Day by controlling the candidates," Schier said, adding that Republicans are watching closely with the aim of portraying Walz as "Captain Gaffe."

By avoiding missteps, the Democratic ticket is making Trump the issue because they're not making news beyond what they've carefully chosen to present, Schier said.

He said Trump's approach is the opposite. Schier described it as, "If I'm just out there all the time, any given comment won't matter."

Hann acknowledged that some Republicans are frustrated that Trump isn't more scripted, but said, "He's not a dictator, he's not the devil. He's a business guy who's going to try to make the country better."

Walz will be in a much less controlled situation Tuesday in the live debate on CBS, giving voters a look at who he is. "It's one of the few times the media gets direct access to the candidate and everybody's watching," Schier said.

Amara said he doesn't expect a knock-out blow from either Vance or Walz, saying the first rule of being a vice presidential candidate is "do no harm."

Walz will need to be prepared to pivot from defense if Vance goes after him on specifics about his handling of the Feeding our Future fraud, his response to the 2020 riots or his departure from the military after 24 years. If Walz "dwells on those things, that would be a mistake," Amara said.

If Walz can be sincere and relaxed, the governor can be appealing to uncommitted voters. "If I'm Tim Walz, I make it a beer vs. wine debate," Amara said. "JD Vance is a very good speaker; charming and folksy he is not."