ALBUQUERQUE, July 19 — A third political party seldom rises to a level much beyond annoyance to Republicans and Democrats. That is clearly not the case in New Mexico, where the Green Party has achieved so much power that its leaders say both major parties this year have tried to exploit it for their electoral advantage. One offer, they said, came from Republicans this month, a promise of at least $100,000 if the Greens fielded candidates in two House races as a way to hurt Democratic chances. The other, they said, came from Democrats in January, a suggestion of helping...