Polls showed Joe Biden maintaining a lead over President Donald Trump as the Democratic National Convention begins.

According to an NBC News/Wall Street Journal survey released Sunday, Biden was up by 9 percentage points.

He is ahead in 11 combined battleground states – Arizona, Colorado, Florida, Maine, Michigan, Minnesota, Nevada, New Hampshire, North Carolina, Pennsylvania and Wisconsin.

Biden is ahead in three Midwest states that voted for Trump in 2016 – Michigan, Pennsylvania and Wisconsin.

However, in a CBS News poll of likely voters nationwide, the former vice president leads by 10 points.

Also, Biden in the RealClearPolitics survey leads by 7.9 points.

An ABC News/Washington Post poll showed that 54 percent of voters endorsed his selection of Kamala Harris as his running mate.

In a new CNN poll conducted by SSRS, Biden was lauded for his choice of Harris.

It showed that 50 percent of registered voters support the Biden-Harris ticket, while 46 percent back Trump and his deputy, Mike Pence.

Reacting to the emergence of Harris as VP candidate, the President had feasted on her comments on fracking, socialized medicine, military funding and tax increment.

Trump also recalled her attacks on Biden, Senator Elizabeth Warren, and Supreme Court Justice Brett Kavanaugh.