After the 2016 election, Democratic leaders reached an all but unanimous conclusion: to defeat Donald Trump in 2020 - they would have to do more than condemn his offensive behaviour and far-right ideology, as Hillary Clinton had done.

They would need, above all, to promote a clear and exciting agenda of their own.

They took that lesson to heart in the midterm elections and afterward, capturing the House of Representatives with a focus on health care and then attempting to impress the electorate by passing legislation on matters like campaign finance reform and the minimum wage.

As Democratic presidential contenders pushed campaigns built on big ideas, House speaker Nancy Pelosi resisted a chorus of calls for impeachment, even from some of her party’s leading 2020 candidates.

Yet 13 months before the next election, Democratic leaders are now steering into a protracted, head-on clash with the US president.

Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Show all 30 1 /30 Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Members of the Proud Boys, a fascist group, jeer at anti-Trump protesters outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter dressed as Uncle Sam poses at Uncle Sam Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A baby blimp rears its head amidst a group of anti-Trump protesters outside the president't campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam President Trump addresses supporters at the launch event of his 2020 election campaign in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Proud Boys have adopted Fred Perry polo shirts as their uniform and many members have the name of the group tattooed on their arms Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A line of police officers separate opposing groups of protesters outside the launch of President Trump's 2020 campaign launch Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A protester hits a Trump punching bag during a protest outside Trump's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Twin Trump supporters pose for a photo at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A protester dressed as a caricature of Donald Trump stands outside the president's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Trump supporter faces off against a protester outside the president's campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Proud Boy shouts across the police line at anti-Trump protesters outside the president's campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Trump supporter poses for a photo at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Proud Boy jeers at anti-Trump protesters who are separated from the president's supporters by a police line outside the president's campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A man dressed as Uncle Sam poses at President Trump's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester faces off against a supporter outside the president's campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Members of the Proud Boys, a fascist group, jeer at anti-Trump protesters outside of the president's 2020 campaign launch Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A child holds a 2020 US "dollar bill" that features Donald Trump's face at the president's 2020 campaign launch EPA Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Anti-Trump protesters rally outside the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Anti-Trump protesters rally outside the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Numerous baby Trump balloons are raised in protests outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter wears a T-shirt depicting Trump as a hero at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam President Trump addresses supporters at the launch event of his 2020 election campaign in the Amway Centre in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester calls for the president to be impeached outside the launch event for his 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Supporters of Donald Trump face off against protesters outside of the president's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A baby blimp rises behind a group of anti-Trump protesters outside the president's campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter dressed as Uncle Sam poses at President Trump's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A member of the Proud Boys, a fascist group, holds a sign up outside of the president's 2020 campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter bears a Trump flag at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Protesters hold baby Trump balloons in the rally outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester holds a sign accusing the president of being a traitor Getty

Ms Pelosi has indicated she aims to move the process along with haste, in part to avoid an election-year conflagration, but the exact course of the inquiry is impossible to foresee.

All 19 Democratic presidential candidates now support the impeachment inquiry, and many party members are optimistic that voters will as well, because Mr Trump is so unpopular and the allegations against him are grave and easily grasped.

For now, Republicans are the party on the defensive, flummoxed by the cascading disclosures about Mr Trump that have threatened to upend his re-election campaign.

But there is also a general recognition, at every level of the Democratic Party, that impeachment could complicate their candidates’ efforts to explain their policy ideas to the country and persuade voters they have a vision beyond ousting Mr Trump.

The party has been disappointed too many times, its leaders say, by betting that the president’s violations of political and cultural norms would bring about his downfall.

Ms Pelosi declared at a conference of New Jersey Democrats in Atlantic City that she would not allow the 2020 election to become a campaign about impeachment.

Insisting the inquiry “has nothing to do with the election”, she said the campaign would be fought on other terms.

“That’s about facts and the constitution,” she said of the impeachment process. “The election is about all of the issues and policies that we have a difference of opinion with the Republicans on, and they are very drastic — and they have nothing to do with impeachment.”

Rudy Giuliani says he is willing to testify over Trump impeachment claims

Ms Pelosi has already advised the newest members of her caucus — the ones who secured the majority last year — that they will have to execute a careful balancing act in the coming weeks, to show voters in their districts that they can continue to pass important legislation.

Rudy Giuliani says he is willing to testify over Trump impeachment claims

She is said to be particularly focused on a proposal to lower prescription drug prices that she unveiled last week, before the Ukraine saga began.

But even before impeachment, House Democrats were gaining little traction with policy bills that withered in the Republican-controlled Senate.

Polls have shown their proposals to be popular, but they have been routinely overshadowed in the news by Mr Trump.

The Democrat challengers to Trump in 2020 Show all 25 1 /25 The Democrat challengers to Trump in 2020 The Democrat challengers to Trump in 2020 Bernie Sanders The Vermont senator has launched a second bid for president after losing out to Hilary Clinton in the 2016 Democratic primaries. He is running on a similar platform of democratic socialist reform Getty The Democrat challengers to Trump in 2020 Joe Biden The former vice president recently faced scrutiny for inappropriate touching of women, but was thought to deal with the criticism well and has since maintained a front runner status in national polling EPA The Democrat challengers to Trump in 2020 Elizabeth Warren The Massachusetts senator is a progressive Democrat, and a major supporter of regulating Wall Street Reuters The Democrat challengers to Trump in 2020 Amy Klobuchar Klobuchar is a Minnesota senator who earned praise for her contribution to the Brett Kavanaugh hearings Getty The Democrat challengers to Trump in 2020 Michael Bloomberg Michael Bloomberg, a late addition to the 2020 race, announced his candidacy after months of speculation in November. He has launched a massive ad-buying campaign and issued an apology for the controversial "stop and frisk" programme that adversely impacted minority communities in New York City when he was mayor Getty Images The Democrat challengers to Trump in 2020 Tulsi Gabbard The Hawaii congresswoman announced her candidacy in January, but has faced tough questions on her past comments on LGBT+ rights and her stance on Syrian President Bashar al-Assad Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Pete Buttigieg The centrist Indiana mayor and war veteran would be the first openly LGBT+ president in American history Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Deval Patrick The former Massachusetts governor launched a late 2020 candidacy and received very little reception. With just a few short months until the first voters flock to the polls, the former governor is running as a centrist and believes he can unite the party's various voting blocs AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Beto O'Rourke The former Texas congressman formally launched his bid for the presidency in March. He ran on a progressive platform, stating that the US is driven by "gross differences in opportunity and outcome" AP The Democrat challengers to Trump in 2020 DROPPED OUT: Kamala Harris The former California attorney general was introduced to the national stage during Jeff Sessions’ testimony. She has endorsed Medicare-for-all and proposed a major tax-credit for the middle class AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Bill De Blasio The New York mayor announced his bid on 16 May 2019. He emerged in 2013 as a leading voice in the left wing of his party but struggled to build a national profile and has suffered a number of political setbacks in his time as mayor AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Steve Bullock The Montana governor announced his bid on 14 May. He stated "We need to defeat Donald Trump in 2020 and defeat the corrupt system that lets campaign money drown out the people's voice, so we can finally make good on the promise of a fair shot for everyone." He also highlighted the fact that he won the governor's seat in a red [Republican] state Reuters The Democrat challengers to Trump in 2020 DROPPED OUT: Cory Booker The New Jersey Senator has focused on restoring kindness and civility in American politics throughout his campaign, though he has failed to secure the same level of support and fundraising as several other senators running for the White House in 2020 Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Wayne Messam Mayor of the city of Miramar in the Miami metropolitan area, Wayne Messam said he intended to run on a progressive platform against the "broken" federal government. He favours gun regulations and was a signatory to a letter from some 400 mayors condemning President Trump's withdrawal from the Paris Climate Accord Vice News The Democrat challengers to Trump in 2020 DROPPED OUT: Kirsten Gillibrand The New York Senator formally announced her presidential bid in January, saying that “healthcare should be a right, not a privilege” Getty The Democrat challengers to Trump in 2020 DROPPED OUT: John Delaney The Maryland congressman was the first to launch his bid for presidency, making the announcement in 2017 AP The Democrat challengers to Trump in 2020 DROPPED OUT: Andrew Yang The entrepreneur announced his presidential candidacy by pledging that he would introduce a universal basic income of $1,000 a month to every American over the age of 18 Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Julian Castro The former San Antonio mayor announced his candidacy in January and said that his running has a “special meaning” for the Latino community in the US Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Marianne Williamson The author and spiritual adviser has announced her intention to run for president. She had previously run for congress as an independent in 2014 but was unsuccessful Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Eric Swalwell One of the younger candidates, Swalwell has served on multiple committees in the House of Representatives. He intended to make gun control central to his campaign but dropped out after his team said it was clear there was no path to victory Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Seth Moulton A Massachusetts congressman, Moulton is a former US soldier who is best known for trying to stop Nancy Pelosi from becoming speaker of the house. He dropped out of the race after not polling well in key states Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Jay Inslee Inslee has been governor of Washington since 2013. His bid was centred around climate change AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: John Hickenlooper The former governor of Colorado aimed to sell himself as an effective leader who was open to compromise, but failed to make a splash on the national stage Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Tim Ryan Ohio representative Tim Ryan ran on a campaign that hinged on his working class roots, though his messaging did not appear to resonate with voters Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Tom Steyer Democratic presidential hopeful billionaire and philanthropist Tom Steyer is a longtime Democratic donor AFP/Getty

There is little doubt that impeachment will become a singular obsession in the political world and dominate news coverage for as long as the inquiry is underway.

A few early polls on impeachment suggest that public support for the inquiry is somewhat stronger than opposition to it, but those numbers could easily change in either direction as the process unfolds.

Diane Feldman, a Democratic pollster, said it would be difficult for the party to communicate with voters on issues besides impeachment for the duration of the process.

But candidates up and down the ballot had to try to drive a message about policy all the same, she said.

“I think it’s worth the effort, but it’s a long shot,” Ms Feldman said. “That we not put all of our eggs in the impeachment basket seems to me extremely wise.”

However, she said the impeachment process could also “add some clarity to risks that Trump presents to our national security and foreign policy” and sharpen the overall Democratic case against his re-election.

The task of balancing impeachment against policy priorities will be especially delicate for lawmakers elected last year, including dozens who won narrow victories in historically Republican districts.

Democrats are defending a sizeable number of seats that Mr Trump carried in 2016, in parts of the country like upstate New York, Oklahoma City and northern Maine, where the impeachment issue is likely to stir backlash.

Congressional Republicans are likely to struggle in a different way, as they face pressure from their party’s conservative base to defend Mr Trump even as he behaves in erratic or legally questionable ways.

Democratic presidential candidates are attempting their own juggling act, mixing denunciations of Trump’s actions on Ukraine with detailed policy promises.

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Mr Biden, the candidate most directly connected to the impeachment uproar, has repeatedly denounced Mr Trump, but has declined to reorient his activities around responding to the president.

Senator Elizabeth Warren of Massachusetts, Mr Biden’s leading competitor in the primary, has reminded voters this week that she was the first major Democratic candidate to demand Mr Trump’s impeachment.

But she, too, has not dwelled on the subject in her speeches, and she has indicated she would prefer to avoid a sprawling, open-ended process.

And at the same Democratic gathering in New Jersey where Ms Pelosi spoke Friday, senator Cory Booker urged his party to avoid “partisan glee” about the prospect of impeaching Mr Trump.

Talking to reporters outside the event, he said Democrats should keep campaign considerations separate from impeachment: “It’s just something that I need to deal with in a very sober way,” he said, “away from politics.”