At the 2005 Chilean presidential and congressional elections, I noted the unique (as far as I know) feature of a multiparty alliance having separate presidential candidates despite joint congressional lists on the same day. In that case, the alliance with the odd pattern was the right-wing Alianza.
But maybe they were just setting a trend. Even as the Concertacion, the ruling alliance of the Christian Democrats, Socialists, and other center-left parties, has selected its presidential candidate (Christian Democrat and ex-president Eduardo Frei) and is geting ready to form its congressional lists, a Socialist is collecting signatures for a possible “independent” first-round presidential bid. Greg Weeks has the details.