Life, as Donald Trump has known it for the last two years, has just changed forever. Quagmired in a government shutdown of his own making, Trump’s ability to manipulate his world is already severely constrained in this very new year. The more he struggles against his new surroundings, the more he sinks.

Last week the president could only watch his beloved cable news channels as a bystander to the biggest tectonic shifts, as the Democrats took control of the House of Representatives and Senator Elizabeth Warren became the first candidate to officially emerge to run against him next year. And it won’t be long before the House launches several investigations into corruption and incompetence, while the Mueller investigation continues to tighten several nooses around all things Trumpian.

Outside Trump’s wall of delusion and distractions, there is a host of strong women candidates poised to join Warren

So it may be early, but it’s not too soon to survey who is best placed to eject Trump from the White House, if indeed the 45th president makes it that far.

It’s no coincidence that the first candidate to emerge against Trump – and enrage him – is a woman. Warren, the Massachusetts senator, represents at least two constituencies that have driven grassroots politics over the last decade.

That is something Trump should recognise from his own campaign. Almost every US election since 2006 has been defined by a wave of voters seeking change, especially in the shape of a new candidate promising to reform a broken system.

Nancy Pelosi swept to power as House speaker first in 2006 amid the disaster of President Bush’s second term, and she returned this week to the same position promising adult supervision of an even more calamitous Republican. Each cycle in between – with the exception of Obama’s reelection in 2012 – has seen the same dynamic of turfing out incumbents in the pursuit of hope and change.

Warren has long given voice and academic heft to the argument that the root cause of the broken system is a broken economy, skewed by Wall Street and the super-wealthy. But on that basis, as with most other policies, she will find herself in a crowded space with most of the other Democrats who will join her in this contest.

Play Video 0:51 Trump says he may declare national emergency over US-Mexico border wall – video

The second factor propelling Warren’s candidacy is the dramatic political turn in November’s midterms: the sharp shift among women voters. Democrats held a 19-point advantage among women, according to the exit polls, six points higher than two years earlier. In particular, Democrats moved from a nine-point loss among white women to parity with Republicans as married women shifted allegiance.

This is not a trend that Trump knows how to stop. In fact, his reaction to Warren’s candidacy only underscores his limited grasp of the shifting political realities that kicked his own party out of power late last year. He told Fox News this week that “you’d have to ask her psychiatrist” to know if Warren believes she can win, and he continued to troll her on Twitter about her Native American family roots.

Outside Trump’s wall of delusion and distractions, a host of strong women candidates is poised to join Warren. Kirsten Gillibrand of New York and Amy Klobuchar of Minnesota have often found themselves entirely misjudged by the men around them. Gillibrand was considered vulnerable in her first Senate election in 2010, but she trounced all comers in all of her contests. Klobuchar proved more than a match for the clumsy bullying of supreme court nominee – now Justice – Brett Kavanaugh last year.

But one likely candidate particularly intrigues. Kamala Harris embodies the driving force pushing Democrats to record turnouts in non-presidential contests over the last two years: women of colour. The California senator has served just two years in Congress – like the last freshman senator to win the Democratic nomination, in 2008. But unlike Barack Obama, Harris has a very significant record of public service in her pre-Senate career, serving as her state’s attorney general for six years and as San Francisco’s district attorney for seven years.

While all the Democratic candidates can appeal beyond their own demographics, personal perspectives can and do influence political character. There’s no mystery about why Trump performs so well with older white men. And there should be no surprise that Harris – the daughter of Indian and Jamaican immigrants – has already won the overwhelming support and respect of influential women of colour who will help shape the Democratic primaries.

Harris, like the other candidates of colour, will face the same questions Obama did in 2008 about appealing to the white working-class voters across the rust-belt states that Hillary Clinton narrowly lost to Trump. However, working-class challenges are most acutely experienced by minorities, and each of the former industrial states that tipped the 2016 election – Pennsylvania, Michigan, Wisconsin – have diverse electorates that shifted decisively against Trump last year.

The test for Harris, and all the other Democrats, is whether she can effectively demonstrate that she is listening and responding to those voters in order to overcome the culture wars that Trump will happily wage. Obama succeeded in 2008 by showing he was the adult in the middle of a financial crisis. He succeeded again in 2012, by showing Mitt Romney was out of touch with economic reality. If anything, Trump fills both boxes even more snugly than his predecessors.

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Well before the general election, the candidates will need to navigate the primary and caucus voters, where Democrats – even in less diverse states like Iowa – tend to be more progressive and want more change, not less. There’s no reason to think a candidate of colour cannot succeed there, where Obama did in 2008. The biggest difference this time around is that the largest state of all has moved forward its primary – with all its nominating delegates – to March, three months ahead of where it used to be. That state, California, is home to Kamala Harris.

All the challengers will claim they can appeal to working-class and middle-class voters with more affordable healthcare and education, and a fairer economy. The key primary test for all candidates will be who can best take the fight to Trump while still talking to voters beyond the reach of his tweets.

In politics they say you should never wrestle with a pig, but the desire to stay clean did little for Trump’s opponents in 2016. Voters expect their candidates to stand up for themselves while still talking about what matters in their lives. The test for the female (and male) candidates of 2020 is how to sling mud without getting stuck in it.

• Richard Wolffe is a columnist for the Guardian US