Joe Biden intended to spend Friday talking about climate change and his long-standing support for the gay and lesbian community.

Instead, he was thrust into the center of the latest White House scandal — that President Trump allegedly urged the Ukrainian president to investigate Biden’s son Hunter.

Suddenly, Biden faced two dueling realities: The president he is hoping to defeat next year — and who he describes as morally unfit for office — is under scrutiny for behavior some view as treasonous. But the story is inextricably linked to Biden’s son, pushing one of the topics that Biden is least comfortable discussing into the spotlight.

The challenge of taking advantage of this political moment without becoming ensnared was evident by how Biden responded to the news Friday afternoon. First, he reacted defensively in an exchange with reporters in Iowa. Then later, in a formal statement from his campaign, he forcefully denounced Trump’s actions.

“Not one single credible outlet has given any credibility to his assertions. Not one single one,” Biden told reporters in Iowa on Friday afternoon, referring to the allegations related to his son, after initially ignoring shouted questions.

“And so I have no comment,” he said. “Except the president should start to, uh, be president.”

He brushed aside further questions about whether Trump had abused his power.

But two hours later, Biden’s campaign released a written statement that was far more robust. While his initial response was to defend his family’s honor, his second statement focused on Trump’s behavior.

He said that Trump’s “clear-cut corruption damages and diminishes our institutions of government by making them tools of a personal political vendetta.” He also called on Trump to release the transcript of the call in question.

“This behavior is particularly abhorrent because it exploits the foreign policy of our country and undermines our national security for political purposes,” Biden said in the statement. “It means that he used the power and resources of the United States to pressure a sovereign nation — a partner that is still under direct assault from Russia — pushing Ukraine to subvert the rule of law in the express hope of extracting a political favor.”

The heightened scrutiny of Trump’s interactions with the Ukrainian leader, and efforts by congressional Democrats to investigate it, thrust the 2020 campaign into uncertain terrain — for Trump and Biden, who leads the polls in a crowded Democratic primary field.

When Biden first entered the presidential race, it triggered a burst of attention on Hunter Biden’s foreign business ties and made-for-tabloid lifestyle.

The Biden campaign had hoped it had dispatched with some of those questions.

That won’t be so easy if House Democrats move toward impeachment proceedings. While the hearings would focus on Trump’s behavior, House Republicans would also amplify questions over Biden’s actions while he was in office.

Several Democratic presidential candidates on Friday condemned Trump without mentioning Biden. Sen. Elizabeth Warren (Mass.) renewed calls for his impeachment and said “by failing to act, Congress is complicit in Trump’s latest attempt to solicit foreign interference to aid him in US elections.” Gov. Steve Bullock (Mont.) called it “behavior you’d expect from an incompetent mobster.”

But the news also comes at a time when some of Biden’s Democratic rivals are growing increasingly desperate to gain traction, and shedding some of their unwillingness to attack him forcefully. And while some may rally behind Biden for what they view as an unfair — and potentially illegal — targeting of a fellow Democrat, it could lead others to question whether he is best fit to counter Trump.

“We’re out there every day criticizing Trump and saying it’s the most corrupt administration in the history of America,” said Grant Woodard, an attorney and longtime Iowa Democratic consultant unaligned with a candidate. “It’s going to be problematic for Biden to have to answer those questions about himself.”

“Whether it’s true or not, the fact that you have to deal with it is problematic. It’s a distraction they don’t want,” he added. “They want to create the narrative, ‘I can win, I can take on Trump, don’t let the perfect be the enemy of the good in terms of ideological fights.’ This is the stuff they don’t want to be talking about.”

Biden allies, meanwhile, hope that elevating the case surrounding Hunter Biden will dispel the notion that he did anything wrong.

It also serves as a vivid example of how worried Trump is about Biden’s prospects in a general election. On Friday night, Biden sent out a fundraising email saying, “Donald Trump asked a foreign leader to investigate me and my family.”

Trump’s campaign has spent months focused on Biden’s family, attempting to cast the former senator and vice president as a lifelong politician whose family has been personally enriched off his powerful positions.

Trump’s lawyer Rudolph W. Giuliani has suggested that Biden improperly used his influence to get Ukraine to dismiss its top prosecutor, Viktor Shokin, in 2016. The prosecutor general’s office had opened an investigation into Burisma Holdings, a national gas company on whose board Hunter Biden had a position starting in April 2014.

Biden traveled to Ukraine in March 2016 and said the United States would withhold $1 billion in loan guarantees unless Shokin was removed.

The push was part of a wider effort — which involved other Western allies as well as the International Monetary Fund and World Bank — to remove Shokin, who was viewed as corrupt.

“We found no evidence to support the idea that Joe Biden advocated with his son’s interests in mind,” PolitiFact wrote in May. “It’s not even clear that the company was actively under investigation or that a change in prosecutors benefited it.”

One of the reasons Biden took a long time to decide whether to get into the presidential race was over considerations of the attacks on his family that not only come under the bright lights of a national campaign but also from the bullying tactics that Trump has employed.

It also comes at a time when his son has become fodder for gossip pages. He divorced his wife amid charges of extramarital affairs, cocaine use and financial problems. He also began dating the widow of his brother, Beau, who died of brain cancer in 2015. After their separation, he married a woman in May that he had met a few weeks earlier.

Biden’s campaign earlier this year declined to say whether it had done a full vetting of Hunter, which campaigns sometimes do to prevent surprises.

During Biden’s announcement speech in Philadelphia, most of Biden’s immediate family appeared onstage with him. Hunter, afraid that being there would be a distraction, did not attend.

He said during a fundraiser earlier in the year that his grandchildren had urged him to run for president and were cognizant of the amount of scrutiny that would come.

“ ‘Mommy and daddy had a divorce and they’re going to really go after that,’ ” Biden recounted hearing from one of his grandchildren. “My generic point is they know how tough it’s going to be.”

Biden was asked last month about the appropriateness of Giuliani’s efforts, and reports that the State Department was cooperating with his efforts to press Ukraine to investigate his son.

“I’m not worried about it,” Biden responded. “But secondly, I think it’s Rudy Giuliani. And it’s the president. And appropriateness has never been the measure they’ve started with.”

When asked about concerns of a quid pro quo, Biden demurred.

“I have no idea what they’re doing,” he said.

Holly Bailey in Cedar Rapids, Iowa, contributed to this report.