Months after telling Hillary Clinton the American people were "sick and tired of hearing about your damn emails," the times may be a-changing for Bernie Sanders as he wages an increasingly intense campaign ahead of California's Democratic primary.

In an appearance on HBO, Mr Sanders, 74, was asked if the furor over Mrs Clinton's use of a private email server as secretary of state had become large enough for the Vermont senator to rethink his refusal to engage on the issue. "It has," he said, adding, "But this is what I also think: There is an enormous frustration on the part of the American people."



The State Department's inspector general found in a report made public on Wednesday that the email set-up violated department rules, that Mrs Clinton never sought permission for it, and that the proposal would have been rejected if she had. The report handed Mrs Clinton's Republican opponents a fresh line of attack – and Mr Sanders, too, if he chose to take it.



Mrs Clinton's competitor for the 2016 Democratic presidential nomination won praise at a candidates' debate on October when he said, "Enough of the emails. Let's talk about the real issues facing America.'' At the time, his campaign used the comments in a fund-raising email.



Fast forward seven months and for Mr Sanders, the delegates on offer on June 7 in California and five other state nominating contests represent a last-ditch effort to close the gap with Mrs Clinton before the Democratic convention in July.



The former secretary of state holds a nearly insurmountable lead in the delegate-amassing contest, and is far ahead in popular votes. But a strong performance in California may boost Mr Sanders' case that superdelegates – party leaders and elected officials not formally bound to any candidate – should switch their allegiance to him on the basis of perceived electability against Republican Donald Trump.



In another sign Mr Sanders has taken off the gloves, his campaign late on Friday demanded the ouster of Connecticut Governor Dannel Malloy and former Massachusetts Representative Barney Frank from a key platform committee at the Democratic National Convention.



The campaign, in a statement, said the pair are "aggressive attack surrogates" for Mrs Clinton, and Sanders' lawyer said Mr Malloy and Mr Frank can't work impartially "while labouring under such deeply held bias."



In a letter hand-delivered to Democratic National Committee late Friday, Brad Deutsch, Mr Sanders' campaign counsel, wrote of animosity by Mr Frank toward Mr Sanders dating to 1991.

The pair's criticisms of Mr Sanders have gone beyond dispassionate ideological disagreement and have exposed a deeper professional, political and personal hostility toward the senator and his campaign, Mr Deutsch said.



Democratic officials rejected Mr Sanders' request on Saturday, the Associated Press reported.

Democratic presidential candidate Senator Bernie Sanders. AP

Also this week, Mr Sanders, keen for network airtime before the California vote, appeared to get a boost when presumptive Republican nominee Trump agreed to debate him to raise money for a charity. The billionaire businessman backed out on Friday, saying it would be "inappropriate" to debate the second-place Democrat.

Bloomberg