Democratic presidential candidate Joe Biden has raised concern after he delivered a confused campaign speech in South Carolina, saying he was a “candidate for the United States Senate” and that people could “vote for the other Biden” if they did not like him.

His speech at the First in the South Dinner on Monday came ahead of the presidential primary in the state on Saturday.

A video of Mr Biden’s speech shared widely on social media showed him saying: “My name is Joe Biden. I’m a Democratic candidate for the United States Senate. Look me over, if you like what you see, help out. If not, vote for the other Biden.”

Mr Biden, 77, has made a series of confusing and controversial statements during a presidential campaign to date that has seen his poll ratings tumble.

Earlier this month, he mistakenly referred to New Hampshire as Nevada on the night of the state’s first-in-the-nation primary.

The speech led some to raise concerns about his health and how rigorous campaigning was affecting him.

Solomon Rajput, a medical student running for Congress in Michigan, said: “The Biden campaign is seriously shameful. Biden was a respectable, if flawed, VP and the yes-men who let his mental health fracture so obviously and extremely like this should be ashamed to their core.

“Take Biden home. Let him retire with dignity. This is sick.”

Another person said: “Whether you’re a Joe Biden supporter or not, I think it’s time for him to drop out… he should be able to retire. Whoever is making him do this is evil.”

Despite the gaffe, Mr Biden has a lead over Senator Bernie Sanders in the latest South Carolina poll of Democratic voters, with both candidates ahead of the pack.

According to figures released by polling firm Public Policy Polling on Monday, Mr Biden has 36 percent of votes, ahead of Mr Sanders who has 21 percent. The firm added Biden was the only candidate with a favourability rating of over 50 percent.

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