WASHINGTON — As Joe Biden prepared to launch his 2020 presidential bid last April, members of President Donald Trump’s inner circle began publicly pushing unsubstantiated allegations about the former vice president and Ukraine.

The president’s eldest son, Donald Trump Jr., and Brad Parscale, his 2020 campaign manager, both blasted out links to articles on Twitter within days of each other in early April that painted Biden and his son Hunter as unethical, based on unproven charges stemming from Hunter Biden's work in Ukraine.

Those first mentions, distributed to their combined millions of social media followers, coincided with a spring effort by the president’s personal lawyer Rudy Giuliani to find damaging information on Biden and preceded, by a matter of days, Trump’s first phone call on April 21 with then Ukrainian President-Elect Volodymyr Zelenskiy.

Four days later, Biden announced his run for office.

The trickle of tweets soon became a steady stream. Over the next four months, Giuliani, Trump Jr., and other top surrogates lobbed accusations at both Bidens at least a dozen times.

By late July, when Trump placed a second call to the Ukrainian leader explicitly asking him to investigate the unfounded claims, the president’s campaign and official super PAC — as well as the Republican National Committee and its chairwoman — had all amplified messages with unverified information about the Bidens and the Eastern European country.

Revelations about Trump’s July call with Zelenskiy in recent days put the early aspersions cast on the Bidens by those eager to re-elect Trump in a new light. A whistleblower complaint also alleges that Giuliani, Attorney General William Barr and others may have assisted with or tried to conceal the president’s attempt to get the Ukrainian government to interfere in the 2020 election by investigating the Bidens.

And Giuliani’s contact with Ukrainian officials and efforts to get them to investigate unproven claims of misconduct by the Biden family — an endeavor he’s said was at the direction of the president and coordinated with the State Department — are now at the center of an impeachment inquiry in the House.

The amplification by Trump’s political allies of the unsubstantiated Biden accusations also suggest any presidential request for an investigation into the former vice president or his family could be a political endeavor, not one aimed at rooting out corruption in Ukraine, as Trump has said.

Trump campaign communications director Tim Murtaugh said it makes complete sense that the president’s political aides would focus on the background of a potential 2020 opponent.

“Hunter Biden’s sweetheart business deals in Ukraine and China are directly linked with his father’s time as vice president and everyone knows it,” Murtaugh said. “We have been talking about this for months. It would be campaign malpractice not to bring this to the attention of voters.”

It’s not the first time that those closest to Trump have shown an openness to political help from foreign actors or dropped clues about significant developments and teased major political implications to come. In 2016, Trump Jr. convened a meeting at Trump Tower with a Russian lawyer claiming to have damaging information about then-Democratic candidate Hillary Clinton.

Months later, Giuliani hinted that the campaign had a “couple of surprises” left, just days before unfavorable revelations about Clinton’s email investigation became public.

Giuliani, an outspoken advocate for the president, has a history of flaunting sensitive information, and the allegations about the Bidens and Ukraine this year were no different, according to two former White House officials.

“He talks to everybody about it,” one official said, including urging campaign officials, outside surrogates and donors to push the controversial narrative.

This summer, the Trump campaign’s main account and even the official Republican National Committee account started tweeting about the Bidens and Ukraine, raising questions about how widespread the tactic extended beyond the Trump White House.

The president has argued his conversations with Zelenskiy were intended to eliminate corruption, but a review of Trump’s top surrogates shows a much more targeted approach when it comes to spreading harmful stories that could ultimately hurt his political opponent heading into 2020.

In early May, the official Trump-backed Super PAC posted a Tweet linking to a story with the following headline: “HUNTER BIDEN’S WORK IN UKRAINE EMERGES AS A POTENTIAL 2020 SCANDAL.”

In June, about a month before the president’s second call with Zelenskiy, Trump’s campaign tweeted an imaginary executive order “preventing Joe Biden from steering sweetheart foreign deals to family.” It even included a directive to sign up for campaign text alerts.

Trump Jr. sent at least five tweets between April and August dealing with Hunter Biden’s business arrangements in Ukraine, often linking to stories with damning banners, including: “Eight Things to Know About the Biden Family's Culture of Corruption”

On June 20, GOP chairwoman Ronna McDaniel tweeted: “Weeks after Joe Biden traveled to China and Ukraine as VP, his son cashed in on millions of dollars in foreign money. Even Democrats are calling it a “huge” conflict of interest. Biden needs to come clean about abusing his role as America’s top diplomat.”

Even the president retweeted several messages on Biden and Ukraine earlier this year, including one by former Gov. Mike Huckabee calling out “Biden’s cushy deals w/ Ukraine and China,” ending simply with “#Enough.”