Joe Biden’s recent surge in the Democratic primary has revived his White House hopes and, with them, the Senate GOP’s interest in using their power to dig into his son Hunter’s business dealings in Ukraine.

The desire for dirt on the Bidens was what prompted House Democrats to impeach President Donald Trump, after it was revealed he was leveraging military aid to Ukraine as part of his efforts. But as Biden seemed to fade from contention during the early voting contests, interest in Hunter Biden’s time on the board of a Ukrainian energy company called Burisma seemed to fade among Trump and Republicans too.

That’s now changed. On the heels of Biden’s string of primary wins on Tuesday, GOP lawmakers are teeing up letters and subpoenas for new information on the Bidens. And they’re offering up a fresh explanation for why the push is justified: they’re just vetting the guy for the benefit of Democratic primary voters.

“If he is in fact the frontrunner for the Democratic nominee to be president of the United States,” said Sen. Kevin Cramer (R-N.D.), “all the more reason to get to the bottom of it, and make sure that the people have all the information that they need to make an informed decision on the person that would be president of the United States.”

The de facto leader of the Biden investigations, Sen. Ron Johnson (R-WI), told reporters on Wednesday that Biden has not “adequately answered” questions about his family’s involvement in Ukraine, despite no actual evidence of wrongdoing on the part of the former VP.

“[I]f I were a Democrat primary voter, I’d want these questions satisfactorily answered before I cast my final vote,” he said.

On Monday, Johnson announced that the Senate oversight panel, which he chairs, would be moving forward with a subpoena for documents and testimony related to Hunter Biden’s service on the board of Burisma. And in the same breath he raised unanswered questions about the Bidens, the Wisconsin senator insisted that going after them was not his intention. “My investigations are not focused on the Bidens,” he said. “They just aren’t. But I can’t ignore them, because they’re part of the story. They made themselves part of the story... they made themselves part of this issue of legitimate investigation.”

The idea that Republican lawmakers are providing a public service to Democratic primary voters was treated as absurd by Democrats on Wednesday. Instead, they saw the renewed interest in Hunter Biden and Burisma as a not-particularly-subtle attempt to tar Joe Biden by association—raising questions about his integrity that don’t need to be asked right as the general election is approaching.

“Get ready,” said Sen. Chris Murphy (D-CT), who has traveled with Johnson to Ukraine on several occasions. “The Senate is going to turn into an arm of the Trump campaign. I don’t think we’ve expected anything different. The President is willing to use all the official powers at his disposal to try to destroy his political rivals. The Senate Republicans gave him a pass on that, and thus it stands to reason they would attempt to do some version of the same thing.”

The president’s allies allege that Biden, when he was vice president, corruptly endeavored to protect his son Hunter’s business dealings in Ukraine by working to oust a Ukrainian prosecutor who was looking into corruption at Burisma. But that prosecutor, Viktor Shokin, had put those investigations aside. And while much was made by Republicans of Biden’s push to get rid of him, the Obama administration and U.S. allies wanted to see him gone, too, because he was seen as insufficiently committed to fighting corruption.

Neither U.S. nor Ukrainian officials ever filed criminal charges against the Bidens, and the former Ukrainian prosecutor general, Yuriy Lutsenko, said in May 2019 that there was no evidence of wrongdoing. The Bidens themselves have denied wrongdoing, too.

“We already knew that Donald Trump is terrified of facing Joe Biden—because he got himself impeached by trying to force a foreign country to spread lies about the Vice President on behalf of his re-election campaign,” said Andrew Bates, a spokesman for the Biden campaign. “Now, Senator Johnson just flat out conceded that this is a ham-handed effort to manipulate Democratic primary voters.”

President Trump himself remains closely in touch with some of the most central figures off Capitol Hill trying to trigger investigations of the Biden family and Ukraine. On Wednesday, the president’s personal lawyer Rudy Giuliani told The Daily Beast that he was still in regular contact with Trump.

Asked when the two of them last spoke, the Trump attorney replied, “yesterday”—the same day Biden dominated Super Tuesday’s Democratic contests and dramatically improved his chances of securing the party’s 2020 presidential nomination.

Giuliani would not divulge the nature or subject matter of their Tuesday conversation. But the former New York mayor and leading Biden antagonist had previously vowed, following Trump’s acquittal in the Senate impeachment trial, to continue to probe the Bidens and Ukraine issues.

As The Daily Beast reported last month, Giuliani has done so at the explicit encouragement of his client, with Trump, post-acquittal, privately urging his attorney to keep digging on the matter and to keep the president updated on whatever progress he makes.

In early February, Giuliani said he was planning on “ramping up” his probes into Joe and Hunter Biden, claiming that “it’s a matter of the fair administration of justice for real.”

In the Senate, that ramping-up was timed nicely with Biden’s reemergence in the Democratic race. On Sunday, the day after Biden’s comeback win in the South Carolina primary, Johnson sent a letter to members of his committee notifying them of plans to hold a vote on a subpoena for Andrii Telizhenko, a former Ukrainian diplomat who worked for a consulting firm, Blue Star Strategies, that represented Burisma in the U.S.

In his letter, Johnson wrote that he is “convinced obtaining Mr. Telizhenko’s Blue Star documents and information is an important part of this investigation.” Telizhenko, reported The Daily Beast in November, has ties to Trumpworld figures like Rudy Giuliani, and helped spread the narrative popular among the president’s allies that Ukrainian officials meddled in the 2016 election to hurt Trump.

A vote on the subpoena is scheduled for Mar. 11. If approved, it will be the first subpoena issued by Senate Republicans for anything related to Burisma. Asked to respond to allegations of fishy timing, Johnson scoffed. “They’re just wrong,” he said on Wednesday.

The top Democrat on Johnson’s committee, Sen. Gary Peters (D-MI), declined to say to reporters if he felt that the probe is politically motivated. He did oppose it, however, on the grounds it was a waste of time: “This investigation should not be part of what we're doing at Homeland Security,” said Peters. “There are too many other important issues that impact the security of our country.”