Donald Trump is under severe pressure after a disastrous run which saw his impeachment defense shredded by current and ex-officials and, most stunningly, by his own acting White House chief of staff.He must also placate fellow Republicans on whom he will depend to save his presidency in any Senate trial, after triggering self-inflicted crises over Syria and the G7 summit that tested his party’s tolerance for its volatile leader.Every Monday over the month since House Speaker Nancy Pelosi initiated an impeachment inquiry, it seemed like life could not get much worse for an increasingly isolated President.Yet every week it does.At times, as his simmering fury bursts open in meetings or on Twitter, and as new political conflagrations take hold, it looks like Trump’s presidency is unraveling. And, perhaps worse, a hollowed out White House can’t cope with the incoming fire.Read MoreThe signs are not great that things will improve for Trump in the week ahead, however, with a new battery of State Department officials expected to testify to three Democratic committees taking depositions in the impeachment inquiry about Trump’s alleged abuse of power on Ukraine.G7 walk backThe President did defuse one potential political nightmare over the weekend — backing off plans to hold next year’s G7 summit at one of his Florida resorts, after his initial announcement caused outrage and claims of blatant self-dealing and corruption.In a tweet, Trump blamed the “Do Nothing Democrat/Fake News Anger” for his reversal. But there is little doubt that his move was made to spare GOP lawmakers the pain of defending the President in a controversy entirely of his own making.”People think it looks lousy,” acting White House chief of staff Mick Mulvaney said on “Fox News Sunday” before adding to his accident-prone streak with a comment that could be interpreted as meaning the President had never really distanced himself from his business empire — as he promised to do.Trump reverses course and says his Florida resort won’t be used for G7 summit “(Trump) still considers himself to be in the hospitality business,” Mulvaney said.There is so far no suggestion that Republican support for the President over impeachment is waning. But his Syria withdrawal — seen by many Republicans as a betrayal of America’s Kurdish allies — is testing patience for the President in his own party, perhaps more than any other previous incident.On Friday for instance, Senate Majority Leader Mitch McConnell penned an unrestrained Washington Post op-ed in which he branded Trump’s Syria withdrawal “a grave strategic mistake.” Some Republicans told CNN last week they were alarmed at the President’s mood and behavior. When Mulvaney told reporters to “Get over it” amid claims that foreign policy in Ukraine was being motivated by hopes of a political payoff, the White House’s hubris appeared out of control.The President’s apparent disdain for the price Republicans pay for supporting Trump reflects confidence that the GOP base, over which he holds a firm grip, is an infallible insurance policy. He certainly lapped up the adoration of the Trump faithful in a pair of rallies last week.But his retreat over the G7 summit may indicate that the President also understands there may be some issues on which his usually pliable party will not accommodate him.New danger from fresh testimonyA new parade of current and former US officials are expected to trek up to Capitol Hill this week, raising the prospect of offering testimony that could further damage the President.They could include the top US diplomat in Ukraine Bill Taylor possibly as soon as Tuesday. The career foreign service officer was thrust into the public eye following the release of his text exchanges with former Special Envoy for Ukraine Kurt Volker and ambassador to the European Union Gordon Sondland.In the exchanges, Taylor expressed concern about foreign policy moves being tied to political motives, writing that it was “crazy to withhold security assistance for help with a political campaign.”Testimony from former and current State Department officials has appeared to play into Democratic hands and deflected White House efforts to stall the investigation.More on the impeachment inquiry from CNNTrump impeachment inquiry: A visual timelineTrump’s Ukraine scandal: Who’s who?The phases of Trump’s coming impeachment proceedingsTrump’s Ukraine phone call, annotatedKey allegations from the Ukraine whistleblower are true, despite what Trump saysThe Ukraine text messages, annotatedShocking revelations over the last week already appear to indicate that the President set up an off-the-books foreign policy operation to deal with Ukraine. At its center was his personal attorney Rudy Giuliani who was mining the former Soviet Union for dirt on the potential Democratic 2020 rival that aides said the President feared the most — former Vice President Joe Biden.A lack of leaks from the committees from Republicans with mitigating information to offset revelations from official testimony, has darkened the picture for Trump.It appears more and more that the whistle blower report and the rough transcript of Trump’s July 25 call with Ukrainian President Volodymyr Zelensky is just the tip of the impeachment iceberg.Democrats charge that Trump abused his power by using his prerogative to dictate foreign policy to force a leader abroad to procure negative information on a political opponent.That’s exactly what did happen — according to Mick Mulvaney last week.The former South Carolina congressman on Sunday tried — and largely failed — to walk back his brazen comments made during a calamitous Thursday White House briefing. “That’s not what I said. That’s what people said I said,” Mulvaney protested on “Fox News Sunday” before being shown video evidence of his implication that there was indeed a quid pro quo in Ukraine.Secretary of State Mike Pompeo also denied that there was any quid pro quo offered by the White House in holding up military aid while it was seeking political help from Ukraine.”I never saw that in the decision making process,” he said on ABC News’ “This Week.”But GOP Rep. Francis Rooney, who has not ruled out supporting impeachment, told CNN’s Jake Tapper on “State of the Union” on Sunday that Mulvaney could not walk back his previous comment.”I would say, game, set, match on that,” Rooney said.Mulvaney on shaky ground, source saysTrump, after having spent the weekend apparently watching news coverage of Mulvaney’s appearance and frenetically tweeting, is becoming frustrated with his top White House official, CNN reported. Mulvaney may already have been on thin ice, since the President’s son-in-law and senior White House adviser Jared Kushner had been trying leading efforts to to oust him before the impeachment drama erupted. While Kushner has fielded complaints about Mulvaney, an administration official insists Kushner did not reach out to any potential replacements for the chief of staff job.In a source’s view, Mulvaney is increasingly on shaky ground with Trump, but by no means is it clear that the President will get rid of him.Mulvaney faced White House ouster threat before impeachment crisis took overThe optics sure wouldn’t be great. It would mean yet another chief of staff in about three years.The latest reports of discord in the White House reinforce a growing impression that Trump’s advisers are not up to the task, or have lost the capacity to contain his wildest impulses.On two occasions last week White House gambits were turned back against the President by mocking adversaries.A photo of Pelosi upbraiding Trump in a private meeting with congressional leaders was quickly embraced by the Speaker who seized on it to suggest she overpowered the President.Then, the White House apparently leaked a letter from Trump to Recep Tayyip Erdogan written in juvenile language that the Turkish President later treated with disdain.If details seeping out of the impeachment committees about the breadth of the evidence are confirmed, Trump’s defenders may find it difficult to support his claims that his call with Zelensky was “perfect” or that offenses that are inappropriate from a President did not take place.They may be forced to fall back on a less politically satisfying defense that the President’s activity was wrong, but does not merit the bar of high crimes and misdemeanors required for him to be ejected from office.