Second term (2017–2023)
Johnson's politics became more right-wing during his second term and he expressed support for various political conspiracy theories. He was a close ally of the Trump administration, though he disagreed with the administration on economic issues because of its willingness to increase government spending. Johnson initially opposed the Tax Cuts and Jobs Act in 2017, feeling it was too generous to larger corporations and did too little for small businesses, and he objected to how the bill would affect companies using a pass-through model, but he was successful in getting a 20% deduction in taxation for pass-through businesses. When accused of benefiting from the tax breaks, he said it benefited him because tax breaks benefit everyone.
As chair of the Committee on Homeland Security and Governmental Affairs, Johnson launched investigations into several people associated with the Obama administration, including Clinton and Vice President Joe Biden's son Hunter Biden. Johnson probed Hunter Biden's involvement with Ukraine and the contents of his laptop but did not present evidence of wrongdoing. He pressed the issue even after many in his party had abandoned it. He had some Republican support, but critics from both parties accused him of using the issue to spread Russian disinformation and gain support for Trump's reelection. Johnson himself was among the most prominent targets of ethics investigations by the Democratic Party. He was accused of abusing flights to Florida and of giving his chief of staff $280,000 in violation of Senate rules. The flights complaint was dismissed, and Johnson justified the payment as a personal gift for the recipient's cancer treatment.
After the 2018 Wisconsin elections, Johnson was the only Republican holding statewide office in Wisconsin and came to be seen as a leader of the state's Republican Party. He attributed that year's Republican defeats to a lack of grassroots organization or work with local political groups. Johnson criticized Senate Republicans for prioritizing their political careers over enacting conservative policy and pushed them to take stronger positions, especially on repealing the ACA. Republicans negotiated with Johnson to gain his support for a more limited rollback of the policy, including an argument between Johnson and Senate Majority Leader Mitch McConnell on the Senate floor. Johnson eventually agreed, but the bill was unsuccessful. Johnson's approval rating in Wisconsin began falling in 2019.
In 2021, during the Biden administration Johnson delayed passage of the American Rescue Plan Act. He forced a reading of all 628 pages of the bill on the grounds that the Senate had not had enough time to read it. The same year, he voted against funding highways and transit programs through the Infrastructure Investment and Jobs Act and called the trial of Derek Chauvin for the murder of George Floyd a distraction from immigration issues.
Johnson voted to confirm Neil Gorsuch, Brett Kavanaugh, and Amy Coney Barrett to the Supreme Court and voted against the confirmation of Ketanji Brown Jackson. In 2022, he blocked a Biden administration nominee, William Pocan, from serving as a federal district court judge in Wisconsin despite previously endorsing him.
In January 2018, Johnson said an informant had told him that the FBI and Department of Justice had conspired against Trump after he won the 2016 presidential election. He agreed that the Russian government likely interfered in the election, but he opened investigations into the FBI investigation of the Trump campaign's dealings with Russia, said Congress should have handled the special counsel investigation into Russian interference, and said that Robert Mueller, who headed the special counsel, should not have been involved because he was a former FBI director.
Johnson accused FBI members of forming a "secret society" that held secret meetings, referencing the use of the term in text messages between FBI officials Peter Strzok and Lisa Page. Along with several other Congressional Republicans, he called for a special counsel to investigate the FBI. The FBI contacted Johnson in August 2020 to warn him that the Russian government might use him to spread disinformation. Johnson said they could not provide any details and accused them of organizing the briefing so it could be leaked to make him look bad.
In 2019, Trump was impeached over allegations that he had frozen aid to Ukraine to pressure the Ukrainian government to announce investigations into whether Ukraine had interfered in the 2016 presidential election and whether Joe Biden had interfered in an investigation involving his son, although the claims had already been found to be false. Johnson called the impeachment an attempt to sabotage the Trump administration, singling out Lieutenant Colonel Alex Vindman for testifying against Trump, and co-sponsored a resolution to condemn the impeachment inquiry.
Johnson was heavily involved with Ukraine–United States relations due to his positions as vice chair of the Senate Ukraine Caucus and chair of the Foreign Relations Subcommittee on Europe and Regional Security. He had been involved in discussions of aid to Ukraine and tried to dissuade Trump from freezing it. Johnson reported that he "winced" when he learned from ambassador Gordon Sondland that the freeze was tied to the request for investigations, but he accepted Trump's denial of the allegation. Johnson had also spoken to former Ukrainian diplomat Andrii Telizhenko, who alleged that the Ukrainian government interfered in the election by cooperating with the investigation into Trump's 2016 campaign chairman Paul Manafort. Johnson endorsed the prospect of investigations into Biden's activity in Ukraine and China so long as the investigation did not involve pressuring a foreign government.
Johnson chose not to recuse himself from the impeachment hearing despite his close involvement, saying his recusal would prevent Wisconsin's citizens from having an equal say in the result. He offered to testify, which raised questions about the protocol of a senator providing testimony and then voting based on that testimony. He also provided a statement to House Republicans detailing his involvement. Johnson ultimately voted against having witnesses testify at all.
Johnson voted to acquit Trump because the impeachment resolution did not accuse him of a crime. He dismissed the United States Government Accountability Office's decision that Trump broke the law, saying its findings were a political dispute between the executive and legislative branches of government.
During the COVID-19 pandemic, Johnson rejected the accepted medical understanding of COVID-19 and its treatment. He expressed support for the COVID-19 vaccine but said its importance was overstated. He spread false claims about potential dangers of the vaccine, citing user-submitted reports of the Vaccine Adverse Event Reporting System to say thousands of people had been killed by the COVID-19 vaccine despite the Centers for Disease Control and Prevention finding evidence that only three deaths might have been caused by the vaccine out of 245 million doses; Johnson's communications advisor later walked back the claim. He opposed the use of vaccine passports to document vaccination and a provision in the 2022 defense bill that mandated the discharge of servicemen if they did not receive the COVID-19 vaccine.
Johnson accused the media of hiding alternative treatments to COVID-19 such as hydroxychloroquine and ivermectin, which were found to be ineffective. He brought several witnesses before the Committee on Homeland Security and Governmental Affairs to testify against the medical consensus, including Jane Orient, who disputed the vaccine's efficacy, and Ramin Oskoui, who falsely said that face masks, quarantining, and social distancing are ineffective in reducing spread of the virus. YouTube suspended Johnson from the platform for seven days after he uploaded a video touting unproven treatments for COVID-19. He was also critical of preventative measures like lockdowns and face masks, encouraging caution in imposing limitations that could affect essential functions while acknowledging that distancing measures were important in flattening the curve.
Johnson opposed the spending increases implemented during the pandemic, including the Paycheck Protection Program, though he voted for the CARES Act stimulus program. When the Senate considered a Biden-backed stimulus bill—the third since the pandemic began—Johnson invoked a procedural stalling tactic requiring the bill to be read in its entirety in the Senate chamber, which remained mostly empty during the reading. He opposed extending the pandemic's higher unemployment benefits in 2021 out of concern that it would create a perverse incentive to keep people from working.
In the lead-up to the 2020 presidential election, Johnson declined to say whether he would recognize the results as legitimate, and said the supporters of whoever lost would reject the results. He warned that Democrats would riot if Biden lost but said Republicans would not riot if Trump lost. He also accused the Democratic Party of misconduct for implementing more lenient policies for postal voting and drop-off voting.
After Biden won, Johnson planned on objecting to the electoral results. He withdrew his objections to certifying the results after Trump supporters attacked the Capitol Building during the election certification on January 6, 2021. Johnson argued the attack was not a significant threat to the Senate's safety and said he would have been be more afraid if Black Lives Matter or Antifa had been at the Capitol, saying he knew Trump supporters and they never "would have done what the rioters did"; this prompted accusations of racism. He accused the FBI of knowing about the attack before it occurred and claimed without evidence that it had been provoked as a false flag attack. Although police radio confirmed that people were armed, Johnson argued that it was not an "armed insurrection" because no weapons were seized. Johnson opposed the second impeachment of Donald Trump that accused Trump of causing the attack, saying impeachment would merely "inflame the situation".
Despite voting to certify the election, Johnson continued to spread disproved claims about widespread election fraud and sought investigation into the allegations, saying there was "voter fraud that the mainstream media and, unfortunately, many officials just simply ignore" and that Democrats had "gamed the system" in Wisconsin. In private, Johnson said he knew Biden had won legitimately, and he eventually recognized Biden's victory publicly. He walked back his claims of voter fraud, saying it was not widespread enough to invalidate Biden's victory. Of his investigations, he said his intention was to investigate irregularities and not to overturn the election.
In May 2021, Johnson voted against creating the January 6 commission to investigate the attack. Andrew Hitt, the chair of the Republican Party of Wisconsin in 2021, testified to Congress that Johnson had suggested submitting electoral votes for Trump despite Biden's victory in Wisconsin. Johnson defended his involvement as limited to only a few seconds when he introduced his staff to one of Trump's lawyers.
The House January 6th Committee revealed that Johnson's aide Sean Riley texted Chris Hodgson, an aide to Vice President Mike Pence, to request that Johnson personally give Pence an envelope containing fraudulent alternate electors for Michigan and Wisconsin. Hodgson refused. In 2023, the FBI collected phone records of Johnson and eight other Republicans documenting the times and recipients of their calls on January 4–7, 2021, to investigate their involvement in the plot to submit fake electors and overturn Biden's victory. Johnson decried this as inappropriate surveillance by the Biden administration.
