The Trump International Hotel, Washington D.C. Janhvi Bhojwani | CNBC

Before President Donald Trump's controversial phone call with the president of the Ukraine, Volodymyr Zelensky's closest advisors established contact with Washington, D.C., power players, including former senior administration officials. Prior to their election victory on April 21, Zelensky's campaign hired Signal Group Consulting, a lobbying firm that was initially paid at least $60,000 to set up meetings with government officials, according to a lobbying disclosure report. A little-known U.S.-based attorney named Marcus Cohen helped coordinate these private gatherings. He paid Signal for its services. One of those meetings took place at the Trump International Hotel in Washington, which has become a hub for business leaders and foreign dignitaries to stay when they are in town to meet with members of Congress or the administration. It occurred just months before Trump's now infamous July phone call with Zelensky that has led to an impeachment inquiry by Democrats in the House of Representatives. A summary of the call shows Trump asking Zelenksy if the Ukrainian leader can look into former Vice President Joe Biden and his son Hunter.

Representatives from the countries of Saudi Arabia, Turkey, Malaysia and Nigeria have all stayed at the hotel. Executives from T-Mobile spent $195,000 at Trump International when they were lobbying for their merger with Sprint. T-Mobile has argued that its Trump hotel expenses only represented 14% of its total spent at Washington-area hotels. Ethics experts have argued that the hotel is an example of Trump's business seeing a financial benefit from his presidency. The Citizens for Responsibility and Ethics recently filed a lawsuit against Trump for failing to disentangle himself from his hotels and other businesses, making him vulnerable to inducements by officials seeking to curry favor. The dinner with Zelensky's aides took place on April 16 at the hotel's BLT Prime and featured Mike Rubino, a former Trump campaign advisor and an ex-representative in the Health and Human Services department, and Matt Mowers, who worked for the State Department, according to those familiar with the matter. Former White House press secretary Sean Spicer also made an appearance at the gathering but shortly left as he had a previous engagement. Executives from Signal were present at the dinner as well.

Former White House Press Secretary Sean Spicer Brochstein/SOPA Images/LightRocket via Getty Images) Michael Brochstein | LightRocket | Getty Images

The focus of the dinner was on the Zelensky campaign and did not break off into a discussion of an investigation into the Bidens, according to those with knowledge of the gathering. "Honestly, I think Signal was trying to impress them," Rubino said in an interview. "I just did it as a favor. I showed up, sat down, ate dinner and left. I didn't really speak to anybody because they spoke in a different language," he said in explaining the reason he took part in the dinner. Rubino added that it was only later that he learned the Ukrainians at the meeting were members of Zelensky's team. Spicer described his presence as brief and that he was introduced to a member of Zelensky's campaign but could not tell if it was their organizations leader. "They introduced me to the campaign guy," Spicer said in an interview. "I had every impression that they [Signal] were trying to impress this client," he added. People familiar with the event said one of the executives from Signal who attended was Mark Duffy, the group's executive vice president. A spokesman for Signal reiterated that there was no discussion about investigating the Bidens at any of their April meetings involving Zelensky's advisors. "Signal Group facilitated a number of meetings for Mr. Cohen and the Servant of the People campaign in Washington," John Procter, the firm's spokesman, said in a statement. "At no time during the delegation's April visit was there any mention of an investigation of the Biden family or any related topic."