A federal watchdog report on Thursday found that the Trump administration illegally withheld security assistance to Ukraine, and some Republicans quickly settled on a strategy in response: try to discredit the watchdog.

To the extent that Republicans in the administration and on Capitol Hill have responded to the report, few addressed its substantive findings that the Trump White House violated a federal statute when it held up military aid to the U.S. ally. Instead, some have accused the Government Accountability Office, the nonpartisan agency that issued the report, of being in league with Democrats or trying to score some publicity related to the impending impeachment trial against President Donald Trump.

The report’s timing could not have been worse for Trump and his congressional allies, coming as it did just hours before the House of Representatives officially transmitted two articles of impeachment to the Senate, where a trial is expected to start early next week.

Trump’s most vocal defenders quickly leapt into action to try to undercut the report.

“The ‘nonpartisan’ GAO is run by someone confirmed to a 15 year term in 2010 under a Democrat President, Democrat controlled Senate and Democrat House,” tweeted Rep. Lee Zeldin (R-N.Y.), an ally of the president. “Just like Pelosi, Schiff and the Dems in Congress, the GAO ignores that the President has been hugely concerned about corruption in Ukraine for a long time, which is entirely consistent with US law and US policy,” Zeldin added. “It’s also important to get other nations to contribute more.”

In fact, the GAO did not ignore the Trump administration’s policy considerations with respect to Ukraine, it simply concluded that, under a law called the Impoundment Control Act, the executive cannot withhold congressionally appropriated funds for policy reasons, as Trump’s White House did. The White House’s Office of Management and Budget disputed the report’s findings.

Minutes after The Daily Beast published a story on the report detailing those findings, a senior administration official sent an unsolicited email accusing the office of gratuitously injecting itself into the impeachment debate.

After dubbing the report an “attempt to insert themselves into the media’s controversy of the day,” the official sought to undercut GAO’s findings by pointing to instances in which the agency had reversed the findings of reports on similar topics.

“GAO has a history of the flip-flops, reversing 40-years of precedent this year on their pocket rescission decision, they were also forced to reverse a legally faulty opinion when they opposed the reimbursement of federal employee travel costs,” the official wrote. “In their rush to insert themselves in the impeachment narrative, maybe they’ll have to reverse their opinion again.”

Other Republicans settled on a different rhetorical tack: sure, Trump may have violated federal law, but so did Barack Obama.

“Reminder to the mainstream media,” tweeted Rep. Bradley Byrne, this isn't the first time

@USGAO released an opinion that a president broke the law.” The Alabama Republican linked to a 2014 story on a GAO report concluding that Obama’s Defense Department violated a congressional appropriations law by freeing inmates from the Guantanamo Bay prison complex in exchange for the release of Army Pvt. Bowe Bergdahl.

“Remember when House GOP decided to impeach Obama and halt productivity for months because GAO ruled he broke the law?” tweeted Rep. Jim Banks (R-IN) sarcastically, linking to the same story. “Good times.”

On the Senate side, most Republicans—who on Thursday morning were on their way to be sworn in as jurors in the impeachment trial—resorted to a familiar answer to late-breaking bad news about Trump: they hadn’t seen it.

The GOP chairman of the Senate Appropriations Committee, Sen. Richard Shelby of Alabama, was in that camp, though he told reporters he planned to review the GAO report.

But Shelby, a 30-year veteran of the Senate, cast some doubt on the agency’s credibility. “We work with GAO some—they’re not always right,” he said. “A lot of times you frame the issue to GAO, hoping they will give you the desired answer. We’ve all done that, you know, and I don’t know what happened here.”

Others tried to downplay the finding that Trump broke the law by situating it in the normal push-and-pull of executive-congressional relations. “I think this is an institutional argument,” said Sen. Lindsey Graham (R-S.C.), a key Trump defender during impeachment. “At what point does the commander in chief’s authority to control funds clash with the direction by Congress? I think this thing’s been going on for quite a while.”

Despite that, many of these long-serving legislators could not recall a time that GAO issued a similar report. “I have no idea how many similar GAO reports have been issued over the last 20 years about various administration activities,” said Sen. Roy Blunt (R-MO). “I doubt if I’ll consider it significant, but we’ll look at it and see.”