Biden wins Idaho primary: US network projections

Former vice president Joe Biden has swept the Idaho state Democratic primary in his fourth straight victory of the evening over Bernie Sanders, according to US news networks.

Biden had a seven-point lead over the Vermont senator with 96 percent of the vote counted, CNN reported early Wednesday.

His wins in Tuesday's other state contests -- Michigan, Missouri and Mississippi -- put Biden solidly ahead of Sanders in the race.

Before Tuesday's primaries, Biden had already racked up 670 delegates in earlier primaries, compared to Sanders's 574.

With more than half the 57 primary contests still in front of them, a candidate needs to top 1,991 delegates to capture the nomination.