I just ran a search for "worst president ever" and at the bottom of the page Google helpfully added:
Searches related to: worst president everworst president ever sticker impeach bush
How "impeach bush" is related to "worst president ever" as opposed to, say "carter national malaise thermostat police gas lines 444 days of hostages hamas and hezbollah apologist", I have no idea.
BTW, that Carter search doesn't suggest trying "worst president ever".
MORE: Ooh! Ooh! Add "voter disenfranchisement" to that Carter search string. The guy is a peanut farmer -- he really ought to know when to stop digging...