Joe Biden, 76, repeatedly stumbled over numbers and phrases throughout his second Democratic presidential primary appearance Wednesday night, at one point accidentally endorsing one of his primary rivals.

Biden told viewers that if they agree with him, "go to Joe 3-0-3-3-0." He likely meant to tell them to text the number 30330, which subscribes supporters to text message Biden campaign updates.

Near the beginning of the Detroit debate, Biden said that California Sen. Kamala Harris' plan on "Medicare for all" single-payer healthcare "in 10 years will cost $3 trillion," misstating estimates that find "Medicare for all" would cost $32 trillion over a decade.

The former vice president, who spent 36 years in the U.S. Senate before another eight as vice president, later gave a different figure in line with popular estimates: "My plan costs $750 billion. That's what it costs. Not $30 trillion."

In his closing remarks, Biden warned that "eight more years of Trump will change America in a fundamental way," despite President Trump being constitutionally limited to one more four-year term after 2020. It was a flub of a frequent Biden campaign line: "Four years of Donald Trump would be an aberration in American history. Eight years will fundamentally change who we are as a nation."

While sparring with New Jersey Sen. Cory Booker on criminal justice reform and Biden's support for the 1994 crime bill, Biden accidentally referred to Booker as the future president.

"The fact is that the bills that the president, excuse me, the future president, that the senator is talking about, are bills that were passed years ago and they were passed overwhelmingly," Biden said.

"Well first of all, I'm grateful that he endorsed my presidency already," Booker said in response.

At one point, Biden said that he wanted to put "insurance executives who totally oppose my plan in jail for the 9 billion opioids they sell out there." He likely meant pharmaceutical company executives.

Calling for immediate action on climate change, Biden said, "We're responsible for 15% of all the pollution in the country." Tech entrepreneur Andrew Yang correctly stated the statistic shortly later, that the U.S. accounts for about 15% of global emissions.

When discussing the Trans-Pacific Partnership trade deal, he said "TTP" rather than the correct acronym, "TPP."