The undercurrent of rage that has been driving US politics for the past few years surfaced in a series of suspected bombs sent to prominent Democrats and the news outlet CNN less than two weeks before congressional elections.
None of the devices went off and no injuries were reported but top Democrats were quick to label the threats a symptom of a coarsening brand of political rhetoric promoted by President Donald Trump, who also condemned the acts.
"For years now, Donald Trump has been calling for the jailing of his critics and has lauded violence against journalists," said US Representative Bill Pascrell, a New Jersey Democrat.
"The danger of right-wing extremism cannot be ignored and more attention must be paid to it before even worse violence occurs."
Police intercepted six suspected bombs sent to targets including Trump's 2016 presidential rival, Hillary Clinton, former president Barack Obama and prominent political donor George Soros.
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During his presidential campaign, Trump regularly urged his supporters to chant "Lock her up", a threat to jail Clinton, and also supported conspiracy theories that Soros plays an underhanded role in influencing US politics.
Trump has also disparaged the mainstream media and criticised CNN as "fake news".
A recent Reuters/Ipsos poll found rising anger would be a factor driving voters on the November 6 elections when Democrats are seeking to regain control of at least one of the two chambers of Congress.
Politicians from both major parties have made condemning the harsh tone of politics part of their everyday stump speeches.
Republicans have criticised Democrats and liberal activists as a "mob," decrying protesters crowding the US Capitol to oppose Trump's Supreme Court nominee Brett Kavanaugh, and confronting and chastising Republican lawmakers in restaurants and other settings.
Republicans, including Trump, condemned the failed attacks.
"Acts or threats of political violence of any kind have no place in the United States of America," Trump said at the White House.
"We're extremely angry, upset, unhappy about what we witnessed this morning and we will get to the bottom of it."
Senate Democratic leader Chuck Schumer and House Democratic leader Nancy Pelosi dismissed Trump's words, saying they "ring hollow".
"Time and time again, the President has condoned physical violence and divided Americans with his words and his actions," their statement said.
