(Reuters) - Public impeachment hearings for U.S. President Donald Trump next week will mark a historical moment in political television both because of the high stakes and how people will watch the proceedings.

FILE PHOTO: U.S. President Donald Trump is seen in a television camera viewfinder as he speaks at the Shell Pennsylvania Petrochemicals Complex in Monaco, Pennsylvania, U.S. August 13, 2019. REUTERS/Jonathan Ernst/File Photo

The public inquiry into the Ukraine scandal will be the first impeachment hearings of the social, two-screen era, when viewers scroll platforms like Twitter or Facebook while simultaneously watching TV.

Networks expect huge audiences. The Trump inquiry follows seven decades of televised hearings that attracted viewers across the political spectrum.

Here are the highlights:

1951: Gangsters and Gamblers

In 1951 Tennessee Senator Estes Kefauver, who chaired the Senate Committee to Investigate Crime and Interstate Commerce, oversaw televised hearings on interstate gambling with testimony from reputed gangsters. An estimated 30 million viewers tuned in.

1973: Watergate

ABC, CBS and NBC rotated daily coverage of the 1973 Watergate hearings, which led to the resignation of President Richard Nixon. Public television broadcast all 250 hours of the hearings — which 71% of Americans watched live, according to Gallup.

1987: Oliver North and the Iran-Contra affair

Lieutenant Colonel Oliver North’s testimony about the illegal sale of weapons to Iran and support of the Contra rebel groups was carried by ABC, NBC and CBS commercial-free.

1991: Clarence Thomas confirmation hearings

An estimated 20 million people watched law professor Anita Hill testify that she was sexually harassed by Supreme Court nominee Clarence Thomas when she worked for him in the 1980s. The Senate confirmed Thomas by a vote of 52 to 48.

1998: President Bill Clinton impeachment vote

The Dec. 19, 1998 House of Representatives vote to impeach President Bill Clinton drew the highest TV ratings of any day that year, according to the New York Times. Nearly 6 million viewers watched on cable networks CNN, MSNBC and Fox News. The Senate later acquitted him.

2015: Hillary Clinton Benghazi hearing

On October 22, 2015, 4 million viewers across the three cable news networks watched Republican lawmakers question former Secretary of State Hillary Clinton over her efforts to secure the American diplomatic mission in Benghazi, Libya before the 2012 attacks that killed four Americans.

2017: James Comey testimony

About 19.5 million Americans watched Former FBI Director James Comey testify to the Senate Intelligence Committee about his dealings with Trump. Comey said he believed Trump fired him in an effort to undermine an FBI probe into possible collusion between Trump’s presidential campaign team and Russia.

2018: Brett Kavanaugh confirmation hearings

According to Nielsen, more than 20 million people watched testimony by Supreme Court nominee Brett Kavanaugh and Christine Blasey Ford, the woman who accused him of sexual assault. The Senate later confirmed Kavanaugh by a vote of 50-48.

February 2019: Michael Cohen on his ex-boss

The Feb. 27 testimony of Michael Cohen, Trump’s former personal attorney, to the House Committee on Oversight and Reform averaged 15.8 million TV viewers, according to Nielsen.

July 2019: Special Counsel Robert Mueller

An average of 13 million Americans watched the House Judiciary and Intelligence Committees question Mueller about the Russia investigation, according to Nielsen.