CNN  — 

Former Starbucks CEO Howard Schultz announced Sunday that he is “seriously considering” running for president as a “centrist independent” in 2020. Democrats from across the political spectrum reacted with a near universal sentiment: Don’t do it.

The reason is simple: Democrats believe President Donald Trump will be at his more vulnerable in 2020 and see an independent bid by Schultz as a direct threat to defeating the President in a general election match-up.

“It’s easy to get a national poll that makes an independent candidate look competitive, what’s hard is turning that into electoral votes,” said Robby Mook, Hillary Clinton’s campaign manager in 2016. “And where an independent gets electoral votes — if she or he even could get any — would come disproportionately from blue states.”

Despite that 40% of Americas identify as independent according to a CNN poll released in January, Mook added that there is a “huge difference between people calling themselves independents, or even saying they want to support and independent candidate, and actually voting for one.”

And the numbers back that up: When those who don’t identify as Democrat or Republican are asked how they lean, just 10% really identify as true independents with no affiliation or tendency toward one party over the other.

Democrats believe a Schultz bid would be a coup for Trump, especially if it pulled independent voters away from the eventual Democratic nominee and split the anti-Trump vote that has risen since his election in 2016.

Former Housing and Urban Development Secretary Julian Castro, who announced he was running for President as a Democrat earlier this year, told CNN’s Jake Tapper on “State of the Union” Schultz’s possible bid would give Trump the “best hope of getting re-elected.”

Trump’s “only hope… is essentially to get somebody else, a third party to syphon off those votes,” Castro said. “I would suggest to Mr. Schultz to truly think about the negative impact that that might make.”

The United States has a long history of independent candidates running for President, but few have ever come close to winning, especially in recent years as Democrats and Republicans have dominated the two-party system. Ross Perot ran as an independent in 1992, winning close to 20 million votes but no votes in the electoral college.

But their biggest impact is the sense that third party candidates play the role of spoiler. Some Republicans believe Perot cost former President George H.W. Bush the presidency in 1992 by making President Bill Clinton’s path to the White House easier. While some Democrats believe Ralph Nader, who ran as an independent in 2000, cost Al Gore the presidency because his 97,488 votes in Florida helped President George W. Bush beat the former vice president in the decisive state by 537 votes.

History also shows that you don’t have to be a well-known independent candidate to be seen as a spoiler. Although Jill Stein, the Green Party candidate in 2016, got less than 1% of the vote nationally, she won roughly 31,000 votes in Wisconsin, 51,000 in Michigan and 49,000 in Pennsylvania, more than the Trump lead over Hillary Clinton in each of the states.

“It is hard to top Ralph Nader, Joe Lieberman, and Mark Penn on the all-time list of villains, but Howard Schultz is going to give it his best shot,” tweeted Brian Fallon, Clinton’s national press secretary in 2016.

Trump won independents by 4% in 2016, according to CNN’s exit polls, but the voting bloc overwhelmingly backed Democratic candidates – 54% to 42% – in 2018.

Democratic operatives tasked with ousting Trump in 2020 believe that trend could continue in two years, with independent voters – some of whom feel let down by Trump after voting for him in 2016 – backing a Democrat in the president’s bid for a second term.

But a Schultz candidacy could thwart that trend, giving those voters another option and thereby allowing Trump an easier path to victory because of his solidly loyal Republican base.

In response to Schultz’s announcement, many Democrats accused the coffee magnate of a vanity project.

“Any presidential candidate enters the race with a dash of ego and hubris,” said Lynda Tran, a Democratic operative and a founding partner of 270 Strategies. “But a Howard Schultz presidential run would be little more than a vanity campaign that guarantees the most unethical, most unpopular and least qualified president in history wins re-election in 2020.”

She added: “Schultz has to have seen the numbers, has to understand there is no path to the Oval Office for an independent in this political climate and has to know his candidacy would simply cleave off just enough votes to deal a fatal blow to the Democratic nominee.”

Even former New York Mayor Michael Bloomberg, who successfully ran for mayor as an independent in 2009 and is now considering a presidential run in 2020 as a Democrat, suggested that Schultz’s bid was foolhardy.

“The data was very clear and very consistent. Given the strong pull of partisanship and the realities of the electoral college system, there is no way an independent can win. That is truer today than ever before,” Bloomberg said in a statement that did not mention Schultz by name. “We must remain united, and we must not allow any candidate to divide or fracture us. The stakes couldn’t be higher.”

A number of Democrats, especially those on Twitter Sunday night, responded more caustically to Schultz’s possible bid, like Neera Tanden, the President of the Center for American Progress, who said she would call for a boycott of Starbucks if Schultz runs.

Washington State Democratic Party Chair Tina Podlodowski responded by saying: “Just. Don’t.”

Podlodowski, who chairs the Democratic Party in Schultz’s adopted home state, also sent a fundraising email with the subject line “Howard Schultz could secure Trump’s re-election.”

“Howard Schultz running as an independent isn’t about bringing people together,” Podlodowski said. “It’s about one person: Howard Schultz.”

Howard Wolfson, Bloomberg’s top operative, echoed that sentiment.

“I have seen enough data over many years to know that anyone running for POTUS as an independent will split the anti-incumbent, anti-Trump vote,” said Wolfson. “The stakes couldn’t be higher. We can not afford the risk of spoiler politics that result in Trump’s re-election.”

As Democrats lamented the prospect of a 2020 Schultz bid, though, Trump took to Twitter to suggest Schultz doesn’t have what it takes to make a presidential run.

“Howard Schultz doesn’t have the ‘guts’ to run for President,” the President tweeted. “Watched him on@60Minutes last night and I agree with him that he is not the ‘smartest person.’ Besides, America already has that! I only hope that Starbucks is still paying me their rent in Trump Tower!”

CNN’s Jennifer Agiesta contributed to this report.