The speaker was discussing Biden’s recent bragging about working with segregationists and uttered this malaphor. It is a mashup of “to put (one’s) foot in “one’s” mouth” (unintentionally say something foolish) and “have a lead foot” (tend to speed when driving). “Go over like a lead balloon” (utter failure) might also be in the mix, as it seems to fit in context. This one reminds me of the famous malaphor uttered by Ann Richards at the 1988 Democratic Convention, when she referred to George H.W. Bush as someone who “was born with a silver foot in his mouth”. Check that one out in my website at https://malaphors.com/politics/. A big thanks to John Kooser for uttering this one and unabashedly submitting it!