Democrats are embracing an impeachment investigation that could jeopardise their House majority and alienate the suburban voters who have recently warmed to the party and will be vital to defeat President Donald Trump next autumn.

But a growing consensus is emerging among anxious Democrats: The risks are worth it.

Democrats were emboldened by Wednesday’s release of a rough transcript of Mr Trump’s July call with Ukrainian President Volodymyr Zelenskiy, which confirmed the Republican president repeatedly asked a foreign power to investigate his leading Democratic political rival, Joe Biden.

“The guy has got to be stopped,” said Democratic former Virginia Governor Terry McAuliffe, who had previously urged Democrats to move cautiously on impeachment because the Republican-led Senate would almost certainly reject articles of impeachment.

“This is a president using presidential power to invite a foreign government to come into our country and interfere with our democracy,” Mr McAuliffe continued. “This is too much.”

Democrats will face tremendous political peril over the next year, however — a fact underscored by a far more cautious approach from the Democratic governors of Minnesota, Pennsylvania and Wisconsin, who declined Wednesday to endorse House Speaker Nancy Pelosi’s approach.

Trump Intelligence Whistleblower
Speaker of the House Nancy Pelosi speaks to reporters the morning after declaring she will launch a formal impeachment inquiry against Mr Trump (J. Scott Applewhite/AP)

Minnesota Governor Tim Walz, a former congressman, called details of Trump’s phone call “deeply troubling,” but said impeachment may not be the way to go.

“It may not be politically good to do because I think at this point I, like many Minnesotans, am so sick and tired of the dysfunction in DC,” he told reporters.

While Congress’ timeline is unclear, the impeachment inquiry may well run simultaneously with the Democratic Party’s primary election calendar. The first primary votes are scheduled in early February.

Meanwhile, acting Director of National Intelligence Joseph Maguire is set to speak publicly for the first time about a secret whistleblower complaint involving Mr Trump as House Democrats who have read the document say it is “deeply disturbing.”

Mr Maguire is not expected to reveal many details about the substance of the complaint when he testifies before the House intelligence committee on Thursday morning, but House Democrats who are now mulling Mr Trump’s impeachment are hoping he will explain why he withheld it from Congress for weeks.

The complaint from an intelligence community whistleblower, the document which is at the centre the Trump-Ukraine firestorm, was made available to members of House and Senate intelligence committees on Wednesday after Mr Maguire had initially determined they couldn’t see it.

Broadly speaking, the impeachment proceedings will serve as a constant reminder to voters across the political spectrum that Democrats are actively using one of the most sacred powers available to Congress to pursue Mr Trump.

The move is justified but inherently “dangerous,” said Bill Burton, a former adviser to President Barack Obama.

“Nobody knows how the politics are going to play out, which is why it’s so honourable that Speaker Pelosi is moving forward,” Mr Burton said.

“There comes a tipping point where Congress needs to do its job when there’s such blatant abuse of power.”

Strategists in both parties pointed to the electoral backlash against the Republican Party after House Republicans voted to impeach President Bill Clinton in 1998 for obstructing the investigation into his extramarital affair.

Republicans nearly lost their House majority in the next election.

And Democrats, having won a narrow House majority less than two years ago, must now spend the next 14 months protecting vulnerable freshmen in pro-Trump districts to preserve their grip on at least one chamber of Congress.

Polling on impeachment has never been with the Democrats’ new position.

Multiple polls show that a majority of Americans have consistently opposed impeaching Trump. A Quinnipiac University poll released in mid-July, for example, found that 60% of registered voters opposed impeachment proceedings that could lead to Trump’s removal from office; the opposition included 29% of Democrats and 62% of independents.

The context has changed, however.

Previous polling was generally related to the exhaustive investigation into whether Trump conspired with Russia to influence the 2016 election. This one hinges on Trump’s effort to do the same with Ukraine heading into 2020.

The rough transcript released Wednesday leaves no doubt Mr Trump was asking the Ukrainian president to investigate Mr Biden and Mr Biden’s son, who served on the board of a Ukrainian energy company while his father was vice-president.

And while Democrats were outraged by details of the call, the new facts did little to sway Republican officials.

Utah Senator Mitt Romney was among the few high-profile Republicans on Capitol Hill to raise concerns, calling the rough transcript “deeply troubling”.

The vast majority of his Republican colleagues defended Mr Trump’s behaviour.