When the Senate Select Committee on Intelligence holds its next hearing on Russian meddling in the 2016 U.S. presidential election, it will hear from two of the top executives in the tech industry: Twitter CEO Jack Dorsey and Facebook COO Sheryl Sandberg.

Beside them on Wednesday could be an empty seat that's reserved for another high-profile leader. Google CEO Sundar Pichai has so far refused to accept the Senate committee's invitation to show up.

Instead of Pichai, Google offered its top lawyer, Kent Walker, to testify. Walker, the senior vice president of global affairs, is the same guy who previously testified along with Facebook and Twitter's lawyers last year, which was a meek effort from all three companies at a time when Congress and the public deserved to hear from top leadership about how their platforms were so badly abused ahead of the elections.

"Chances are there's going to be an empty chair there," Sen. Mark Warner, D-Va, told CNBC Wednesday, regarding Google's snub of the hearings. "And I think there will be a lot more questions raised that could have been actually dealt with if they sent a senior decision-maker and not simply their counsel."

Warner is the vice chair of the Senate committee.

Google has not said why Pichai or his boss, Alphabet CEO Larry Page, won't accept the committee's invitation. The company declined to comment Friday.

It's a tumultuous time for the world's biggest tech companies, with Facebook taking most of the heat following the reveal of the Cambridge Analytica data scandal in March.

Since then, we've seen Facebook CEO Mark Zuckerberg go through two marathon sessions of weak congressional testimony. We've seen him fumble through a self-inflicted scandal about posting Holocaust denial content to the platform. We've seen him squirm when asked why Alex Jones was still allowed to post bogus conspiracy theories, only to boot Jones off Facebook after a nod from Apple a few days later. We've seen a handful of top Facebook executives, including security chief Alex Stamos, leave the company. And on and on and on.