Vice President Kamala Harris and Gov. Tim Walz debuted their new campaign buses Sunday and kicked off a bus tour of southwestern Pennsylvania ahead of this week's Democratic National Convention.

Upon their arrival on Air Force Two, a few hundred supporters greeted Harris, Walz and their spouses at a hangar where the new were buses parked.

Supporters told ABC News they were thrilled by Harris' candidacy, with one saying she had not felt this excited about politics in years. Some said they had never volunteered for a campaign before signing up to work on Harris'.

"I was excited about Biden, but I am a million times more excited about Kamala," Nicole Molinaro, a Pittsburgh-area mom, said. "I think that we need her leadership. We need her intelligence. We need her progressive, you know, stance. I think we need her experience. We need everything about Kamala."

Another supporter, Edward Freel, said he was unsure about Harris at first, "but then, as I started listening better and following her, [I thought] this woman is going to be good for this country."

During the week of the DNC, Former President Donald Trump and Sen. JD Vance will be out on the campaign trail, holding events in battleground states like Pennsylvania, Michigan, North Carolina, Wisconsin, Georgia, Arizona and Nevada.

Trump allies -- including Sens. Ron Johnson and Rick Scott, and Rep. Byron Donalds -- will travel to Chicago to host press conferences every day of the convention. The Trump team will also give a press conference on Thursday ahead of Vice President Kamala Harris accepting the Democratic party’s nomination.

“As they meet Americans where they are in battleground states across the country, President Trump and Senator Vance will remind voters that under their leadership, we can end inflation, protect our communities from violent criminals, secure the border, and Make America Great Again,” Trump Campaign Senior Advisors Chris LaCivita and Susie Wiles said in a statement.

-ABC News’ Lalee Ibssa, Soo Rin Kim and Kelsey Walsh

Former first lady Michelle Obama will speak at the DNC in Chicago this week, ABC News has confirmed with her office.

Her appearance, first reported by Essence Magazine, will be among a lineup of prominent Democratic leaders who are rallying in support of Vice President Kamala Harris and Minnesota Gov. Tim Walz.

Former President Barack Obama is also scheduled to speak at the DNC.

According to a source familiar with the planning, Michelle Obama will speak on Tuesday -- the same day as the former president.

-ABC News' Michelle Stoddart and Gabriella Abdul-Hakim

Former Democratic Rep. Tulsi Gabbard will assist Trump in preparing for his first debate against Vice President Kamala Harris.

"[Trump] does not need traditional debate prep but will continue to meet with respected policy advisors and effective communicators like Tulsi Gabbard, who successfully dominated Kamala Harris on the debate stage," Trump campaign National Press Secretary Karoline Leavitt wrote in a statement to ABC News, confirming a development first reported by The New York Times.

Gabbard, a former Democratic congresswoman from Hawaii and a one-time Democratic presidential candidate during the 2020 election, gained brief momentum during her presidential run after challenging Harris on the debate stage on topics like criminal prosecutions.

Since leaving the Democratic Party, Gabbard has been gaining traction among Trump supporters, and more recently she has appeared on Fox and other conservative news outlets attacking Harris.

– ABC News’ Rachel Scott, Soo Rin Kim, Kelsey Walsh, and Lalee Ibssa