It was the first time a former president was ever tried or convicted in a criminal case, and was the first of Trump's four indictments to reach trial.
"This is an affirmation that the rule of law works," said Schiff, who represents the Burbank area. "That it can be applied to everyone, including a former president."
Prosecutors accused Trump of falsifying internal business records to cover up hush money payments tied to an alleged scheme to bury stories that might torpedo his 2016 White House bid.
At the heart of the charges were reimbursements paid to Trump's former lawyer Michael Cohen for a $130,000 hush money payment to porn star Stormy Daniels in exchange for not going public with her claim about a 2006 sexual encounter with Trump.
Prosecutors said the reimbursements were falsely logged as "legal expenses" to hide the true nature of the transactions.
"He has really played rope-a-dope in the courts and gotten away with it until today," said Schiff. "I do think justice has finally caught up with Donald Trump. That doesn't mean there won't be appeals and further efforts at delay, but he will be forever branded a convicted felon, and that's a pretty substantial verdict, let alone for a presidential candidate. But I think all of these things, many of which we warned about during that impeachment trial, that if he were not removed from office, he would go on to do worse and worse and worse."
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Moments after he was found guilty, Trump spoke outside the courthouse, calling the trial "rigged."
"This was a disgrace," Trump told reporters. "This was a rigged trial by a conflicted judge who was corrupt. It's a rigged trial, a disgrace."
Schiff believes Trump's comments may be taken into consideration when it comes to his sentencing.
"Every time he goes outside and condemns the court and the jury and the judge, that's going to be taken into consideration at sentencing, because one of the factors the judge is going to consider is, 'Does the defendant accept responsibility?' 'Does the defendant show remorse?' 'Is the defendant willing to pay restitution?' It's quite clear that that is simply not the case with him," said Schiff.
The charges Trump faces are punishable by up to four years in prison. He has denied any wrongdoing and had pleaded not guilty.
Judge Juan M. Merchan has set Trump's sentencing for July 11.
"I think the judge will look at, you know, similar crimes in New York, what kind of sentences have been applied," said Schiff. "So he'll be guided by what generally takes place. Now, this is obviously the exceptional circumstance with the president United States, but I don't think that factor should weigh in. I think he should look at similar defendants, that is, people convicted of similar crimes. What kind of sentence did they get? Did they get jail time? Did they not get jail time? The judge will look at [Trump's] prior record. Now, he doesn't have prior felony convictions, but he has been adjudicated a sexual abuser. He's been adjudicated a business fraudster, and it will depend on New York law whether the judge can consider those things at sentencing, but I think he will get a pre-sentence report from probation and will make a decision based on the facts and what traditionally is handed down in those kind of cases."
Republicans come to Trump's defense
Republicans quickly came to their presumptive presidential nominee's defense.
One of the first reactions came from Ohio Rep. Jim Jordan, one of Trump's staunchest allies in Washington, who called it "a travesty of justice."
"The Manhattan kangaroo court shows what happens when our justice system is weaponized by partisan prosecutors in front of a biased judge with an unfair process, designed to keep President Trump off the campaign trail and avoid bringing attention to President Biden's failing radical policies," Jordan said in a statement. "Americans see through Democrats' lawfare tactics and know President Trump will be vindicated on appeal."
Many congressional Republicans offered a similar response, including Speaker Mike Johnson.
The Associated Press and ABC News contributed to this report.