Rudy Giuliani, President Trump’s personal attorney, said Sunday that his aggressive public campaign against special counsel Robert Mueller’s probe has been successful in turning people against the investigation.

Giuliani, speaking on Fox News' “MediaBuzz,” said public perception will be key to resolving the question of whether the Trump campaign conspired with Russia to meddle in the 2016 presidential election.

“The reality is this is not a court case,” said Giuliani, the former prosecutor and Republican mayor of New York City. “Public opinion will be very important. Think of it this way, they are our jury, our grand jury.”

[More: Rudy Giuliani: No chance Mueller has anything on Trump]

Mueller, Giuliani noted, is likely to follow Justice Department legal precedent that a sitting president can’t be indicted. Mueller is expected to produce reports on his findings, leaving it to Congress to decide how or whether to punish Trump. Lawmakers, in deciding what to do, may be influenced by how the public views Mueller’s probe.

Polls show Republicans in recent months are expressing less support for Mueller’s investigation. In November, about 41 percent of Republicans said they thought Mueller’s probe was fair. In April, that number fell to 26 percent. The vast majority of Democrats have consistently said they support Mueller’s investigation.

[Related: 52% want Russia probe ended, one-third Democrats agree]

“When I came into the case, public opinion was against us,” Giuliani said. “And we got lucky because a lot of bad things have happened to them [the Mueller team] since then. We have utilized that to show what the president has been saying for some time. That this is illegitimate, it’s a witch hunt. I think people are starting to believe it now.”

Mueller's investigation so far has resulted in the indictments of four Trump campaign associates, including the president's former national security adviser Michael Flynn and campaign manager Paul Manafort. The inquiry has also resulted in the indictments of 13 Russian nationals and a dozen Russian intelligence officers for interfering in the 2016 election.