"We're certainly having a conversation about how we hold this president accountable," Swalwell said on ABC News podcast "The Investigation." "I wouldn't say impeachment is off the table."
While Warren and Castro have even announced their support for impeachment proceedings, other key Democrats, including House Speaker Nancy Pelosi, have cautioned against a singularly focused approach.
"While our views range from proceeding to investigate the findings of the Mueller report or proceeding directly to impeachment, we all firmly agree that we should proceed down a path of finding the truth," Pelosi said in a statement on Tuesday. "It is also important to know that the facts regarding holding the president accountable can be gained outside of impeachment hearings."
Trump said Monday he is "not even a little bit" concerned about the possibility of impeachment.
"The Russians will continue to interfere," Swalwell said. "If we don't set some boundaries around what is acceptable conduct for a campaign or a presidency, we could lose our democracy to future interference attacks."
Swalwell, who announced his presidential bid earlier this month, says a full understanding of Mueller's investigation is key to protecting future elections, and that Congress should receive the full report and then determine what information should be released to the public.
"That's how we hold anyone accountable that may not have met criminal culpability, but the Constitution still allows us to hold them accountable," Swalwell said.
He echoed Democratic leadership's calls for Mueller to testify before Congress.
"Let Mueller lay it out," Swalwell said. "Let's hear his voice describe the combat and see where that leaves Republicans and where that leaves the public."
On the matter of obstruction of justice, Swalwell said it's also up to Congress to evaluate the president's actions detailed in the Mueller report and determine what action needs to be taken.
"If we do nothing, what does that mean for future presidencies?" Swalwell asked. "What does that mean for the standard of conduct that we accept in our democracy?"
In the wake of the Mueller report's release, Swalwell also has made numerous calls for Attorney General William Barr to resign, accusing him of favoring Trump and misrepresenting the special counsel's findings by stating there was "no evidence" of collusion between the Trump campaign and Russia. In actuality, the report states that while the investigation "identified numerous links between individuals with ties to the Russian government and individuals associated with the Trump campaign, the evidence was not sufficient to support criminal charges."
"I think," Swalwell added, "he can either be the president's lawyer or America's lawyer."