US Democrats kicked off their four-day national convention on Monday with a call for stronger unity. They saw a turnaround in the race for president, following the withdrawal of Joe Biden and the elevation of Vice President Kamala Harris. They are trying to gain more momentum with the election less than three months away.

About 50,000 people are expected to visit the convention in Chicago. On the first night, delegates will gather to vote on their finalized Democratic Party platform, a statement on their values and policy goals.

Major figures are on the roster of speakers, including Biden and his predecessors Barack Obama and Bill Clinton. Harris' running mate, Minnesota Governor Tim Walz, will also address the convention and Harris is scheduled to speak on the last day.

Democratic National Committee Chair Jaime Harrison described the energy as "through the roof." He added, "The momentum is on our side already and I hope that that wave, that big momentum wave is even bigger coming off of this convention."

Democrats have seen polls start to swing in their direction since Biden dropped out. However, the race is still tight. A survey by RealClearPolitics averaging US polls suggests support for Harris stands at 48.1 percent and former President Donald Trump at 46.7 percent.