Washington | Michael Bloomberg dropped out of the presidential race and backed Joe Biden on Wednesday (Thursday AEDT), throwing the financial might of the Democratic Party's biggest benefactor behind the former vice-president's campaign as Senator Bernie Sanders of Vermont vowed to wage a long battle for the nomination.

Sanders, regarded a week ago as having a clear upper hand over Biden, sounded chagrined after losses in states from Maine to Texas where he was hoping for huge turnout. There was a surge in voter participation, but it lifted Biden instead.