Among whites without college degrees, the core support group that gave him 66 percent of their votes last November, his approval has dropped to 51 percent. White college graduates – a group Trump narrowly carried in 2016 – disapprove rather than approve the president's performance by 54 percent to 42 percent.
Already, those better-educated white voters divide evenly on which party they want to control Congress next year. Overall, Americans by 48 percent to 41 percent say they want Democrats to win back the House. Republican lawmakers have openly warned that a Democratic House in 2019 would set out to impeach Trump.
Additional developments in Mueller's investigation promise to further soften the ground beneath the president and his party. The special counsel's targets include former Trump National Security Adviser Michael Flynn, who was fired earlier this year for lying to Vice President Mike Pence about his own conversations with a Russian diplomat.
Mueller's investigators, as they probe potential obstruction of justice, have also questioned former top White House aides including Reince Priebus and Sean Spicer. They worked for the president when he fired FBI Director James Comey, then leading the Russia investigation, earlier this year.
Monday's news comes at a particularly damaging moment for the president's legislative agenda. Congressional Republicans aim on Wednesday to roll out details of their tax cut plan, which they now call a must-win fight after the earlier failure to repeal and replace Obamacare.
On Twitter, Trump suggested that Mueller timed the developments specifically for the purpose of stopping tax legislation. But on that point, as on his core assertions about Russia, the charges leave the president's battered credibility only weaker.