Article snippet: MORE, stark words that provoked the president and stoked the idea that the former vice president wants to challenge Trump in 2020. “I shouldn’t have said what I said,” Biden told the "Pod Save America" podcast on Friday. “I shouldn’t have brought it up again because I don’t want to get down in the mosh pit with this guy.” Trump responded in kind on Twitter Thursday, writing, “Crazy Joe Biden is trying to act like a tough guy. Actually, he is weak, both mentally and physically, and yet he threatens me, for the second time, with physical assault." “He doesn’t know me, but he would go down fast and hard, crying all the way,” Trump continued in the tweet. “Don’t threaten people Joe!” A White House spokesman did not respond to a request for comment on the president’s tweet. Biden allies say that Trump’s response is a political gift of sorts, and shows that Biden “unnerves the President,” as one Biden World source put it. It’s only heightened speculation that Biden, 75, is serious about challenging Trump. The former vice president sat out the 2016 presidential race, and has heard supporters say he would have defeated Trump if he’d been in the running. Trump triumphed over Democrat MORE by winning the states of Pennsylvania, Michigan and Wisconsin — states Biden sees as practically his political base. Biden is still mulling a Trump challenge. He’s touring the country to promote his book “Promise Me, Dad.” He has also been campaigning for candidates including Conor ... Link to the full article to read more