Friends of the Earth, which created a stir by endorsing Bill Bradley over Al Gore in the Democratic presidential primary, may shun Gore again in the general election and give its backing to Green Party candidate Ralph Nader. FOE President Brent Blackwelder said yesterday that the group has been talking to Nader’s staff. Meanwhile, Nader is mounting what he says is a real presidential campaign, in contrast to his half-hearted run in 1996. This goal is not to win, but to get more than 5 percent of the vote, which would qualify the Green Party for millions in federal campaign matching funds for future elections. A recent poll by the Zogby Group showed Nader getting 5 percent of the vote, more than the 3 percent support for Patrick Buchanan, the likely Reform Party nominee.