Kamala Harris engaged in a Twitter spat with Donald Trump hours after she dropped out of the 2020 presidential race on Tuesday 'with deep regret.'

She and the president traded tweets in the wake of her becoming the biggest name to quit the 2020 field.

Harris cited her campaign's financial woes as a major reason for her exit from the White House race, taking a veiled shot at former New York City mayor Michael Bloomberg and onetime hedge fund manager Tom Steyer as she left.

'My campaign for president simply doesn't have the financial resources we need to continue,' she wrote in an online essay.

'I'm not a billionaire. I can't fund my own campaign. And as the campaign has gone on, it's become harder and harder to raise the money we need to compete.'

Bloomberg did not respond to her attack - but another billionaire did, with Donald Trump tweeting from London, where he is at a NATO summit: 'Too bad. We will miss you Kamala!' prompting her to respond: 'Don't worry, Mr President. I'll see you at your trial.'

She was referring to her next role - as a juror at the almost-certain-to-happen impeachment trial of the president. Democrats in Congress will move towards drawing up articles of impeachment Wednesday.

Clapback: How Kamala Harris and Donald Trump traded insults on Twitter after she quit the 2020 race

How she quit: Kamala Harris' tweet announcing her decision to pull out of the race

Out: Kamala Harris is quitting the presidential race, becoming the biggest name to fall so far. Michael Bloomberg came under fire as Kamala Harris quit, with the California senator pointedly saying: 'I'm not a billionaire. I can't fund my own campaign.'

Show of support: Kamal Harris' husband Douglas Emhoff posted this on Twitter as her decision to quit the race emerged

At her campaign office in Oakland, CA,, staff left a happy birthday message which had been up since October 20, and a wall covered in messages about the candidate.

The decision to quit makes her the biggest name to get out of the 2020 field, and the third to go since Sunday.

Other senators in the race including Michael Benet of Colorado mighty have been more considered more likely to quit before Harris, but her timing appears to be an attempt to avert a catastrophic political meltdown for the first-term senator.

Harris' timing is significant because she wasn't yet registered in her home state as a presidential candidate, and the deadline is December 6.

Polls in California indicated that she would have an anemic showing—an outcome that would signal a slide from juggernaut to weakness.

That could invite primary challengers for her own Senate seat, which she must defend in the 2022 elections.

Harris, 55, struggled to gain traction outside her native California, lagging behind the Democratic pack in poll after poll.

She averaged 3 per cent support. Bloomberg splashed in with 6 per cent this week before he started campaigning.

Some of Harris' aides are leaving her for Bloomberg's newly minted presidential campaign, a source with knowledge of their plans said Tuesday.

The senator had already qualified for the December 19 Democratic primary debate in Los Angeles. Her absence leaves just seven candidates who have cleared the bar.

Tensions: Internal friction between warring camps inside the campaign led cliques to take sides in disagreements between the candidate and her campaign chairman—her sister Maya (right)

The resignation letter submitted by Kelly Mehlenbacher, the former state operations director on Kamala Harris' presidential campaign, says she has 'never seen an organization treat its staff so poorly', after last-minute layoffs

Over and out: Messages left inside Kamala Harris' campaign office in Oakland, California, which had been written when she was running

Not happening: A wall of photographs of Kamala Harris in her campaign office in Oakland, CA

Mood board: Inside Kamala Harris' 2020 campaign office in Oakland, California

Message: Kamala Harris' campaign office in Oakland, CA, which featured one of her viral moments, attacking Joe Biden over school bussing

Message to the candidate: Kamala Harris, who had her 55th birthday in October, is kept up in effigy in her Oakland, CA, campaign headquarters

Dropping out of the White House race will leave two African-Americans in an unusually diverse field—New Jersey Sen. Cory Booker and former Massachusetts governor Deval Patrick. Former Housing and Urban Development Secretary Julián Castro is the lone Latino vying for the Democratic nomination.

Four women remain in the hunt, out of a field of 15 Democrats.

Harris said in an email to supporters that her campaign 'uniquely spoke to the experiences of Black women and people of color.'

And she wrote that despite her lower profile she 'will do everything in my power to defeat Donald Trump.'

Harris would have been the first female president, the second black president and the first president of Indian-American heritage; her mother was born in India.

Harris' campaign seemed already on the ropes when news broke Sunday that her state operations director had quit in mid-November.

Kelly Mehlenbacher left behind a stinging resignation letter (below).

'This is my third presidential campaign and I have never seen an organization treat its staff so poorly,' she wrote.

The Harris campaign, which seemed primed for a boost after the first Democratic debate, had laid off some staff days earlier.

And internal friction between warring camps inside the campaign led cliques to take sides in disagreements between the candidate and her campaign chairman—her sister Maya.

WHAT KAMALA HARRIS EMAILED TO SUPPORTERS AS SHE QUIT Eleven months ago at the launch of our campaign in Oakland I told you all: 'I am not perfect. But I will always speak with decency and moral clarity and treat all people with dignity and respect. I will lead with integrity. I will speak the truth.' And that's what I have tried to do every day of this campaign. So here's the truth today. I've taken stock and looked at this from every angle, and over the last few days have come to one of the hardest decisions of my life. My campaign for president simply doesn't have the financial resources we need to continue. Massive launch: Kamala Harris gathered a large audience for the start of her campaign but since then has cratered I'm not a billionaire. I can't fund my own campaign. And as the campaign has gone on, it's become harder and harder to raise the money we need to compete. In good faith, I can't tell you, my supporters and volunteers, that I have a path forward if I don't believe I do. So, to you my supporters, it is with deep regret -- but also with deep gratitude -- that I am suspending my campaign today. But I want to be clear with you: I am still very much in this fight. And I will keep fighting every day for what this campaign has been about. Justice for The People. All the people. Our campaign has been about fighting for people whose voices have not been heard or too often ignored. We will keep up that fight. Let's remember: we were the first to put the injustice of inadequate teacher pay on the national agenda. We will keep up that fight. We were the first to demand justice for our children, declaring we would take bold executive actions to stop gun violence. We will keep up that fight. We were the first to demand justice for women with a plan to block unconstitutional state abortion laws. We will keep up that fight. Debate: Kamala Harris had already qualified for the December 19 Democratic debate, in Los Angeles; her withdrawal means only seven candidates will be on stage so far And our campaign uniquely spoke to the experiences of Black women and people of color -- and their importance to the success and future of this party. Our campaign demanded no one should be taken for granted by any political party. We will keep up that fight because no one should be made to fight alone. And I believe our campaign showed every child in America -- regardless of their color or gender -- that there are no limits to who can lead and hold positions of power in our country. In that way -- this campaign has been so much bigger than me. I am extremely grateful to the hundreds of staff who moved and uprooted their lives and sacrificed time away from their families. I know our fight has been personal for each of them. Of course I could not have done this without my husband Doug and my entire family and friends who gave up so much to embark on this journey with me and have supported me every step of the way. And I am grateful to the thousands of volunteers and contributors who chipped in, who knocked on doors, who made calls and who put their faith and trust in me. It has been the honor of my life to be your candidate. And I want to be clear: although I am no longer running for President, I will do everything in my power to defeat Donald Trump and fight for the future of our country and the best of who we are. I know you will too. So let's do that together. Let's keep fighting for the America we believe in, an America free of injustice. An America that we know we can be unburdened by what has been. Thank you. — Kamala Advertisement