Trump fires off furious all-caps tweet as Obama warns successor working to 'tear our democracy down'

In raging series of posts, president says of his predecessor: 'HE SPIED ON MY CAMPAIGN, AND GOT CAUGHT!'

Donald Trump issued a series of furious tweets – in all-caps – as Barack Obama delivered a stunning takedown of his successor in a speech at the Democratic National Convention.

The 44th president laid out a thorough rebuke of Mr Trump as he made a pitch for Joe Biden, saying democracy itself was at stake.

Echoing fears among Democrats that his successor has sought to undermine voting rights and vote-by-mail efforts to manipulate the results of the election, he said Mr Trump has shown he will "tear our democracy down if that's what it takes to win".

"This president and those in power are counting on your cynicism," he said. "They know they can't win you over with their policies, so they're hoping to make it as hard as possible for you to vote, and to convince you that your vote doesn't matter. That's how they win. That's how they get to keep making decisions that affect your life, and the lives of the people you love. ... That's how a democracy withers, until it's no democracy at all."

He added: "We can't let that happen. Do not let them take away your power. Don't let them take away your democracy."

The president, whose seething resentment against a president he didn't even run against has seeped throughout his term in office, responded on Twitter, accusing the president of spying on his campaign, part of an "Obamagate" conspiracy that he has promoted following his impeachment.

In a furious series of posts, the president said: "HE SPIED ON MY CAMPAIGN, AND GOT CAUGHT!"

He also suggested that Mr Obama had hesitated to endorse his former vice president and convince him not to run: "WHY DID HE REFUSE TO ENDORSE SLOW JOE UNTIL IT WAS ALL OVER, AND EVEN THEN WAS VERY LATE? WHY DID HE TRY TO GET HIM NOT TO RUN?"

Later he lashed out during Kamala Harris's speech to accept the nomination for Democratic vice-president, writing: "BUT DIDN'T SHE CALL HIM A RACIST??? DIDN'T SHE SAY HE WAS INCOMPETENT???"

From the White House on Wednesday, the president also called his predecessor a "terrible" chief executive and said his "ineffective" two terms were the reason voters put him in the White House four years ago.

"I see the horror that he's left us," he said. "The stupidity of the transactions that he made."

The party's 2020 convention has placed a sharp focus on voting rights, as the president mounts daily attacks against expanding the availability of absentee ballots during the coronavirus pandemic and has appointed a postmaster general who has appeared to have actively sought to undermine the Postal Service in the months leading up to November elections.

The Democrats' 2016 candidate Hillary Clinton also urged voters to overwhelm the ballot box and "vote like our lives and livelihoods are on the line, because they are".

Vice Presidential candidate Kamala Harris, officially nominated as Biden's running mate on Wednesday, kicked off the primetime event to ask: "Why is there so much effort to silence our voices?

"The answer is when we vote, things change," she said. "When we vote, things get better. When we vote, we address the need for all people to be treated with dignity and respect."