BERLIN (AFP) - German Chancellor Angela Merkel won a third term in elections Sunday but her conservatives may be forced to govern in a "grand coalition" with the centre-left Social Democrats, exit polls showed.Merkel's previous junior partners, the pro-business Free Democrats, narrowly failed to re-enter the parliament, ARD and ZDF public television said immediately after polling booths closed.The exit polls gave Merkel's conservatives at least 42 percent, the Social Democrats about 26 percent, but the Free Democrats just below the five percent needed to re-enter parliament.