(Bloomberg) — Donald Trump’s presidency stands on its most treacherous ground after the House voted Thursday to approve and proceed with its impeachment inquiry.The resolution, passed on a largely party-line 232-196 vote, does not just lay out a road map for the public phase of the inquiry. It sends a clear signal that a vote to impeach Trump, and a trial in the Senate, is all but inevitable.Trump becomes just the fourth president to be subject to a formal impeachment effort. Two of them, Bill Clinton and Andrew Johnson, were impeached in the House but weren’t convicted in the Senate. Richard Nixon, facing certain conviction, resigned before the House could vote to approve articles of impeachment.Trump, however, may well become the first president to be impeached and then seek re-election. That dynamic presents a novel challenge for the president, as he must work to keep the Republican Party unified not just to prevent his removal from office by the Senate but also at the hands of voters.Recent moves suggest that Trump understands the peril. After resisting entreaties to add staff to the White House, he is likely to bring on a prominent public relations professional to help with communications on the inquiry, according to people familiar with the matter. His campaign, meanwhile, paid for a glitzy national television ad during game seven of the World Series on Wednesday that highlighted Trump’s accomplishments while criticizing his opponents for “phony investigations.”Partisan ResolutionThe president has become deeply engaged in keeping his party in line. Over the past two weeks, Trump has met face-to-face with more than 60 House members, according to an administration official.No House Republicans voted in favor of the impeachment resolution. One former Republican and fierce Trump critic who left his party this year, Justin Amash of Michigan, voted for it.There is little sign that Trump or his White House plan to suddenly become more cooperative with the impeachment inquiry, even after House Speaker Nancy Pelosi met White House Counsel Pat Cipollone’s demand for a vote to formalize it. And his re-election campaign, the coffers of which are overflowing with cash, is aggressively portraying his opponents as do-nothing politicians obsessed with his removal from office.The campaign paid millions of dollars for a national advertisement during game seven of the World Series on Wednesday that recounted his accomplishments and said Democrats “would rather focus on impeachment and phony investigations, ignoring the real issues.”“He’s no Mr. Nice Guy, but sometimes it takes a Donald Trump to change Washington,” the narrator declares.Sayegh HireWhile Trump has repeatedly dismissed the need to hire additional staff to counter the Democrats’ impeachment efforts, he is likely to bring a former Treasury Department spokesman, Tony Sayegh, into the White House to assist with communications related to impeachment, according to people familiar with the matter. Sayegh’s post will be temporary and he also intends to work on issues other than impeachment, the people said.Sayegh is credited in the White House for helping shepherd Trump’s biggest legislative achievement to passage, the 2017 tax overhaul, and his hiring is supported by the president’s son-in-law and senior adviser Jared Kushner, the people said. They asked not to be identified because Sayegh’s appointment hasn’t been announced.Sayegh declined to comment.Before the House vote, White House counselor Kellyanne Conway said more attorneys and communications staff may “possibly” be added to the West Wing.Trump has no official events on his schedule on Thursday and spent much of the morning tweeting, his preferred channel for responding to the inquiry. He posted more than half a dozen messages ahead of the vote and claimed impeachment is damaging the U.S. economy.“The Greatest Witch Hunt In American History!” he wrote as the House started voting.Weakened ArgumentPassage of the House resolution weakens a central argument for both the White House and allied Republicans: that the inquiry is illegitimate because the House hasn’t held a vote to approve it. The resolution’s adoption may also force Republican members to defend the substance of Trump’s conduct in Ukraine, which most of them have been loath to do.And refusing to participate in the public phase of the impeachment investigation could put Trump at further disadvantage. While Democrats are expected to call a litany of witnesses with damaging accounts of the president’s dealings with Ukraine, Trump would sideline lawyers and aides who might present his defense.“The president has done nothing wrong, and the Democrats know it,” White House Press Secretary Stephanie Grisham said in a statement. “The Democrats want to render a verdict without giving the administration a chance to mount a defense. That is unfair, unconstitutional, and fundamentally un-American.”Trump’s earlier edict to government officials purporting to prohibit them from testifying to Congress or providing records to impeachment investigators has largely been ignored after Democrats issued subpoenas compelling their cooperation. Grisham declined to say in a Fox News interview on Thursday how the White House will handle future requests for testimony and documents now that the impeachment inquiry is formal.“I don’t want to get into any of our strategy just yet,” she said.House Democrats issued a document separate from their resolution that provides the president and his counsel the opportunity to participate in public hearings by responding to claims and requesting their own witnesses. But the White House and House Republicans have said the due-process protections are not strong enough.Trade ComplicationsAs the impeachment battle escalates in the House, Trump will also face added pressure to show his party and the public that he can still govern. The president’s chief argument against impeachment is that he has secured a series of achievements for the country, especially a booming economy — a claim that could be undercut if he becomes bogged down in the investigation and unable to deliver on more of his campaign promises.One of the biggest items on Trump’s agenda is securing a preliminary trade agreement with China, a goal that was complicated by the cancellation of the Asia-Pacific Economic Cooperation summit in Chile, where the president hoped to sign the deal with Chinese President Xi Jinping. Trump tweeted Thursday that both countries are now “working on selecting a new site” for a signing ceremony, which he said would be “announced soon.”But Chinese officials have doubts that there will be a comprehensive long-term trade deal beyond the so-called “phase one” agreement.And the charged political environment surrounding impeachment could complicate the administration’s push to win congressional passage of Trump’s revision of the North American Free Trade Agreement, likely the only remaining chance him to secure a major legislative accomplishment ahead of the 2020 election.The presidential campaign will be dominated by impeachment. The issue may fuel Trump on the trail, where his personal grievances against his opponents are a mainstay of his political rallies. He’ll get his first opportunity to road-test his message after the impeachment vote on Friday, at a rally in Tupelo, Mississippi on behalf of the state’s Republican gubernatorial candidate.“Every American can see this for what it is: an attempt to remove a duly-elected president for strictly political reasons by a strictly partisan, illegitimate process,” Trump campaign manager Brad Parscale said in a statement. “Voters will punish Democrats who support this farce and President Trump will be easily re-elected.”Perhaps, though public polling aggregated by RealClearPolitics shows majority support among voters for the House inquiry. Impeachment also helps to highlight many of Trump’s characteristics that most concern swing voters — his mercurial nature and his willingness to defy conventional expectations of presidential behavior and push the legal limits of his powers.Revelations in the impeachment probe may increasingly alienate voters in America’s political middle who will decide the election. That could force Trump and his team even further toward a strategy he’s already shown that he embraces: aggravating his loyalists’ anger toward Washington and the president’s opponents, in the hope they’ll turn out in force next November — but at the expense of expanding his support.(Updating with Sayegh declining to comment, in 13th paragraph.)–With assistance from Jennifer Jacobs, Josh Wingrove and Mario Parker.To contact the reporter on this story: Jordan Fabian in Washington at [email protected] contact the editors responsible for this story: Alex Wayne at [email protected], Justin BlumFor more articles like this, please visit us at bloomberg.com©2019 Bloomberg L.P.