The Democratic party’s “superdelegates” have every right to overturn the popular vote and choose the candidate they believe would be best equipped to defeat John McCain in a general election, according to Howard Dean, chairman of the US Democratic National Committee.

Mr Dean, who was a presidential candidate in 2004 and is a former governor of Vermont, spoke to the Financial Times just two days after Hillary Clinton put her campaign back in contention with a near double-digit margin of victory over Barack Obama in the Pennsylvania primary.