(The Hill) – Former President Obama is set to hit the campaign trail for Vice President Harris this month, starting his blitz in the key battleground state of Pennsylvania next week.

Obama’s first campaign stop for Harris will be in the Pittsburgh area on Oct. 10, according to a senior campaign official. The former president is then expected to travel to other battleground states in the days leading up to the election.

The former president last month held a solo fundraiser for Harris in Los Angeles, raising $4 million. Obama and former first lady Michelle Obama endorsed Harris less than a week after she took over at the top of the Democratic ticket when President Biden dropped out of the race. Obama was widely seen as having a behind-the-scenes hand in the July pressure campaign for Biden to move aside.

Their endorsement was highly anticipated, as other Democrats rallied around Harris within a few days of her campaign. It finally came in the form of a video showing a phone call from the Obamas to Harris, during which the Democratic couple gave her their support.

Harris and Obama’s friendship goes back 20 years to when they met on the campaign trail as he was running for Senate, the senior campaign official noted. Harris was an early supporter of Obama’s successful 2008 presidential bid and knocked on doors for him in Iowa before the caucus.

The Obamas delivered some of the most memorable speeches at the Democratic National Convention in Chicago in August. The former president called for the nation to move beyond divisiveness while the former first lady took swings at former President Trump in her remarks.

Following Obama’s visit to Pittsburg, the Harris campaign said the former president will make appearances in other key swing states through Election Day, according to the Associated Press.