US President Joe Biden has charged Republican allies of Donald Trump with undermining the country's democratic foundations and urged voters to reject extremism ahead of midterm elections in November.
Biden accused "MAGA forces" - those people devoted to Trump's Make America Great Again agenda - as willing to overturn democratic elections and "determined to take this country backwards" to a time without rights to abortion, privacy, contraception or same-sex marriage supported broadly by Americans.
"Donald Trump and MAGA Republicans represent an extremism that threatens the very foundations of our republic," Biden said on Thursday.
"As I stand here tonight, equality and democracy are under assault. We do ourselves no favour to pretend otherwise."
The prime-time speech in Philadelphia, the birthplace of American democracy, marked a sharp turn for Biden as midterm congressional elections approach.
Thursday's remarks came after speeches in recent days where Biden condemned MAGA philosophy as "semi-fascism" and assailed Republican threats against the FBI after a search of Trump's Florida home as "sickening".
Biden set his remarks in a venue meant to signal the historical significance of his appeal, at Independence Hall, where the US Declaration of Independence and Constitution were adopted.
The speech echoed Biden's signature 2020 campaign pledge to restore the "soul of the nation" and, by implication, purge the values associated with Trump.
In the nearly two years since Biden was elected, Republican voters have mostly backed candidates aligned with the former president, and more than half believe Trump rightfully won the election.
Confronted by threats after Trump's loss, one in five election workers polled this year said they may quit before the next presidential election.