President-elect Donald Trump and the Obama White House traded barbs Thursday over alleged Russian hacking aimed at influencing the U.S. election, with a top Obama aide charging that the cyberthefts hindered Hillary Clinton’s campaign.

Trump fired the first salvo with a morning tweet, declaring that the White House and Democrats were only investigating and talking about alleged Kremlin-backed hacking because Clinton lost an election the party expected to win. The White House shot back later, with Obama’s top spokesman all but saying that Russian President Vladimir Putin was directly involved in the alleged hacking.

Trump used his preferred avenue of communication, Twitter, to make his allegation a day after the White House acknowledged it held off on pointing the finger at the Kremlin before the election out of President Barack Obama’s fear of being seen as trying to help Clinton, whom he had endorsed, while also trying to protect the CIA and other intelligence agencies.

In a tweet posted just before 9 a.m. Thursday, Trump questioned whether the White House would have launched a probe into the hacking if Clinton had won the presidency. He also questioned why the Obama administration announced its investigation last Friday, one month after Election Day.

If Russia, or some other entity, was hacking, why did the White House wait so long to act? Why did they only complain after Hillary lost?

— Donald J. Trump (@realDonaldTrump) December 15, 2016

Trump last week rejected a CIA finding made public in a recent Washington Post report that Russia used hacking to influence the U.S. election.

A Trump aide told reporters on a conference call about two hours after his boss’s tweet that those looking to “delegitimize an election from last month” need to realize its results are going to stand.

Hours later, White House Press Secretary Josh Earnest called it a “basic fact” that candidate Trump publicly urged Russia to hack information that could hurt Clinton. Earnest rejected the transition team’s contention that Trump’s comment was “a joke,” saying national security officials, as well as Republicans and Democrats in Congress, failed to see the humor.

Earnest pointed to an Oct. 7 statement from the U.S. intelligence community as evidence that the Obama administration warned about Russian-backed cyber activity before Election Day. “It wasn’t a secret,” he said. Notably, Obama’s chief spokesman, when asked several times, never denied that the U.S. government has concluded that Putin was involved in the hacking.

Earnest also said there was a reason Trump, in the final weeks of the campaign, told attendees at his rallies to check out hacked Clinton team emails that had been leaked to and later released by WikiLeaks.

He also called it a “fact” that the hacks benefited Trump’s campaign and hurt Clinton’s.

On Wednesday, Earnest called it the “unanimous, high-confidence” conclusion of all American intelligence agencies that the Russian government was involved.

Earnest also said the White House made calculated decisions on when to reveal its hacking findings and the subsequent inquiry to shield U.S. intel agencies from being politicized, which would have occurred, he said, had either been announced during the general election campaign.

“It would’ve been inappropriate for White House figures — including the president of the United States — to be rushing the intelligence community, to expedite their analysis of the situation because we were concerned about the negative impact it was having on the president’s preferred candidate in the presidential election,” Earnest told reporters. “That would’ve been all the more damaging in an environment in which you have the Republican nominee, without evidence, suggesting that the election is rigged.

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“So what we were deeply concerned about from the beginning was making sure that we were protecting the integrity of the intelligence community and insulating the intelligence community from the kind of political pressure that was obvious to everybody who was reading the newspapers or watching television,” he said. “It’s important for our intelligence community to be shielded from that kind of political interference or political influence.”

The Obama administration has vowed a “proportional response” to the alleged hacking, though officials have yet to define what that might look like or if a response has already taken place. On Thursday, Earnest suggested a response has not been delivered, saying the president has a “range” of options that “would be” considered “proportional.”

Even as Trump and his top surrogates continue to signal they will try to pursue warm relations with Russia, Earnest, on Wednesday, wouldn’t rule out sanctions on the country for its actions in Syria before Obama leaves office.

This report was last updated at 3:02 p.m.Contact Bennett at johnbennett@cqrollcall.com. Follow him on Twitter @BennettJohnT