FILE PHOTO: U.S. President Trump speaks at a campaign event in Atlanta, Georgia Reuters

Republican lawmakers have trotted out a series of floundering defenses of President Donald Trump in the wake of evidence of his efforts to pressure Ukraine to launch politically motivated investigations.

This week, those defenses are set to blow up in spectacular fashion.

Several career foreign-service officials are scheduled to testify against Trump — many in defiance of the White House’s orders.

They are expected to give firsthand accounts of his attempts to strongarm Ukraine to deliver political dirt on his rival ahead of the 2020 election.

That testimony would throw a wrench into the Republican Party’s key talking points as it struggles to defend Trump in a rapidly expanding scandal.

Here’s who’s scheduled to testify in this week’s impeachment-inquiry hearings.

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Republican lawmakers have trotted out a series of floundering defenses of President Donald Trump in the wake of damning evidence of his efforts to strongarm Ukraine into delivering him political dirt while withholding military aid and a White House meeting as leverage.

This week, those defenses are set to blow up in spectacular fashion.

The GOP’s flailing efforts to defend Trump during the impeachment-inquiry hearings

The GOP has been grasping at straws to defend Trump in an impeachment inquiry sparked by a whistleblower complaint outlining a July 25 phone call between Trump and Ukrainian President Volodymyr Zelensky.

During that call, the US president repeatedly pressured his Ukrainian counterpart to launch investigations that would benefit his reelection campaign. One would focus on former Vice President Joe Biden and his son, and another would examine a bogus conspiracy theory suggesting it was Ukraine, not Russia, that interfered in the 2016 election in collusion with the Democrats.

A White House summary of the phone call corroborated the whistleblower’s allegations. The intelligence community’s inspector general interviewed several White House officials privy to the call and deemed the complaint urgent and credible.

Trump publicly confirmed that he wanted Ukraine to deliver political dirt by investigating Biden ahead of the 2020 election. And his acting White House chief of staff, Mick Mulvaney, said during a news conference in the White House that the president withheld military aid to Ukraine in part because he wanted Zelensky’s fledgling government to look into purported Ukrainian election meddling.

All this happened before public impeachment hearings. Then, last week, a slate of career foreign-service officers gave damning testimony that the phone call was just one data point in a months-long pressure campaign in which the president leveraged US foreign policy, froze military aid, and held up a White House meeting to strongarm a critical ally into acceding to his personal demands.

These facts alone have made it difficult for Republicans to settle on a consistent defense of the president.

Here’s a small sample of GOP talking points thus far:

There was no quid pro quo.

Even if there were a quid pro quo, countries do that all the time.

It doesn’t matter that Trump initially withheld military aid because Ukraine eventually received it.

Trump was justified in holding up the aid because he wanted Ukraine to investigate its own corruption.

The Democrats colluded with Ukraine.

The witnesses have never spoken directly with Trump, so they’re not credible.

All the witness testimony so far is based on hearsay.

The entire impeachment inquiry is a sham.

Army Lieutenant Colonel Alexander Vindman, a military officer at the National Security Council, center, arrives on Capitol Hill in Washington, Tuesday, Oct. 29, 2019, to appear before a House Committee on Foreign Affairs, Permanent Select Committee on Intelligence, and Committee on Oversight and Reform joint interview with the transcript to be part of the impeachment inquiry into President Donald Trump.(AP Photo/Patrick Semansky) Associated Press

Vindman and Morrison will blow a hole through the GOP’s main defense

On Tuesday, Congress will hear public testimony from Lt. Col. Alexander Vindman, the top Ukraine expert on the National Security Council.

Lawmakers will also hear from Tim Morrison, who oversaw Russian and Eurasian affairs on the NSC until his recent resignation; Jennifer Williams, a senior aide to Vice President Mike Pence; and Gordon Sondland, the US’s ambassador to the EU.

Testimony from Vindman, Morrison, and Williams will be hugely consequential not just because it directly corroborates the whistleblower’s allegations, but because it throws a wrench into Republicans‘ claims that all the accusations against Trump are based on hearsay.

All three officials directly listened in on the July 25 call between Trump and Zelensky that’s at the center of the impeachment inquiry. Vindman also said he witnessed efforts by John Eisenberg, the NSC’s chief lawyer, to bury the White House transcript of the phone call after several officials — including Vindman — sounded the alarm over what they’d just heard.

Former top national security adviser to President Donald Trump, Tim Morrison, arrives for a closed door meeting to testify as part of the House impeachment inquiry into President Donald Trump. AP Photo/Andrew Harnik

Morrison is expected to confirm testimony from Bill Taylor, the US’s interim ambassador to Ukraine.

Last week, Taylor testified that in several conversations he had with Morrison, Morrison conveyed to him that Trump did not want to sign off on any security assistance to Ukraine unless Zelensky committed to pursuing an investigation into Burisma Holdings, the Ukrainian natural-gas company whose board employed Hunter Biden until earlier this year.

Williams, who will testify alongside Vindman, listened in on Trump’s July 25 call with Zelensky and also reviewed a transcript of Trump’s first call with the Ukrainian president, which took place in April, before Pence’s phone call with Zelensky that month.

Williams has testified that Trump’s phone conversation with Zelensky in July struck her as „unusual and inappropriate“ and that Trump’s request that Ukraine’s president investigate the Bidens „shed some light on possible other motivations“ for why he froze military aid to Ukraine.

Pence was given a transcript of Trump’s July phone call with Zelensky before he met with the Ukrainian president in Warsaw in early September. The vice president has said he zeroed in on „corruption“ in Ukraine during his conversation with Zelensky but that he hadn’t had a chance to review the full transcript of the phone call before their meeting.

Meanwhile, Kurt Volker, the former US special representative for Ukraine, is expected to add some color to why the Trump administration had two channels of foreign policy as it relates to Ukraine: a regular channel that consisted of routine diplomacy and discourse, and an irregular channel that consisted of Trump’s allies bullying Ukraine into giving him the political dirt he wanted while withholding military aid and a White House meeting.

Volker’s testimony is especially crucial in this endeavor because he was one of the „three amigos,“ a group of officials with little foreign-policy experience who represented the Trump administration’s main arm in charge of Ukraine policy. The other two were Sondland and Rick Perry, the outgoing energy secretary.

His testimony is also important because, contrary to the GOP’s claims, it establishes that Trump’s policy toward Ukraine was not routine but consisted of a more insidious effort to use the power of his office to get an item of personal value.

U.S. Ambassador to the European Union Gordon Sondland (C) arrives at the U.S. Capitol on October 17, 2019 in Washington, DC. Chip Somodevilla/Getty Images

Sondland takes center stage

Sondland, who will testify beginning at 9 a.m. ET on Wednesday, is expected to be the main attraction in this week’s impeachment hearings.

The hotel executive was given an ambassadorship after donating $1 million to Trump’s inaugural committee and has emerged as the primary link between Trump and Ukraine in the saga so far. Sondland already testified to Congress behind closed doors once but went back and amended his testimony after it was contradicted by Taylor in a closed session.

Since Sondland corrected his testimony to acknowledge a quid pro quo between Trump and Ukraine, Taylor and one of his top aides, David Holmes, have testified that the president and Sondland had a phone call on July 26 during which they discussed that the „big“ topics Trump cared about with respect to Ukraine were the „Biden investigations.“

Sondland apparently had the conversation with Trump while he was out to dinner with Holmes at a restaurant in Kyiv on July 26, and Trump was speaking loudly enough on the phone that Sondland had to hold the device away from his ear. Two officials, in addition to Holmes, are said to have overheard the call.

Because he was in contact with the president throughout the entire Ukraine scandal, Sondland is one of the most significant witnesses against Trump. To that end, his testimony would severely undercut the GOP talking point that none of the witnesses in the impeachment inquiry spoke with Trump personally.

The EU ambassador is widely expected to corroborate Holmes‘ statements in his public testimony on Wednesday. If he does so, it will be the most direct link yet between the president and the push for Ukraine to launch political investigations in exchange for critical US military aid and a White House meeting.

Later Wednesday, Laura Cooper, the deputy assistant secretary of defense for Russian, Ukrainian, and Eurasian affairs, will appear in an open hearing, as will David Hale, the undersecretary of state for political affairs.

Fiona Hill AP Photo/Andrew Harnik

Hill is the eyes and ears inside the White House

On Thursday, Congress will hear from Fiona Hill, the NSC’s former senior director for Russian and Eurasian affairs. She is the official whom Morrison replaced on the council.

Hill is expected to outline how she and John Bolton, then the national security adviser, tried to sideline Sondland as he hijacked Ukraine policy, as well as how they raced to inform the NSC’s lawyer of Sondland’s actions after he used a White House meeting with Ukrainian officials to push Trump’s demand that Zelensky’s administration investigate the Bidens and purported Ukrainian election meddling.

In that meeting, on July 10, Bolton was going „by the book“ before Perry mentioned reforming Ukraine’s energy sector. At that point, Hill said in closed-door testimony, Sondland jumped in and mentioned Burisma, in effect advocating the Trump administration’s shadow foreign policy in Ukraine.

By Hill’s account, Bolton, a longtime lawyer and war veteran, „immediately stiffened“ and cut the meeting short.

Hill recounted Bolton telling her to go to the room in which Sondland, Volker, and Perry met with Ukrainian officials to discuss „next steps.“

„Go down to the Ward Room right now and find out what they’re talking about and come back and talk to me,“ Hill said Bolton told her.

Hill said she heard Sondland discuss how he had an agreement with Mulvaney that the Ukrainians were going to go forward with investigations.

„And my director for Ukraine was looking completely alarmed,“ Hill testified, referring to Vindman.

Hill told Congress that Sondland began to get into discussions with Mulvaney and Rudy Giuliani, the president’s personal attorney, but that she „cut him off because I didn’t want to get further into this discussion at all.“

Afterward, Hill said, she went back to Bolton, who told her to „go and tell Eisenberg that I am not part of whatever drug deal Sondland and Mulvaney are cooking up on this, and you go and tell him what you’ve heard and what I’ve said.“ Hill testified that she conveyed that information to Eisenberg.

Her testimony will be the Democrats‘ final act. Hill will tell lawmakers about her view from the White House into what she saw as a „nightmare“ situation where Trump’s interests were placed above the country’s.