A malaphor, according to Wiktionary, is a blend of malapropism and metaphor; “an error in which two similar figures of speech are merged, producing an often nonsensical result.” The Washington Post‘s Lawrence Harrison apparently coined the term back in 1976.
Luckily for us, Dave Hatfield has been collecting specimens for more than 30 years. (Not surprisingly, most of his examples come from the political sphere.)