Beto O'Rourke on Tuesday again called for President Donald Trump's impeachment — even if it means risking political consequences for his party and even risking his presidential bid, a stance that adds to the number of key Democrats pressuring House Speaker Nancy Pelosi to move forward with proceedings.

O'Rourke, one of the 23 Democrats running for president, said that impeachment proceedings against Trump must begin as "the last resort" when "every other option has failed us."

"We should begin impeachment proceedings against Donald Trump," he said during a CNN town hall broadcast live from Des Moines, Iowa. "[It's] not something that I take lightly. It's an incredibly serious, sober decision."

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He previously called for impeachment proceedings to begin earlier this month, along with a number of other major Democratic presidential candidates.

Pelosi has previously called impeachment the "most divisive" path and has yet to allow House Democrats to move forward with a process that could ultimately lead to Trump's removal from office.

However, as the Trump administration continues to refuse congressional requests for information -- both testimony and documents -- a number of key Democrats are stepping up pressure on the House speaker to loosen her position on impeachment.

Rep. David Cicilline, who is on the Democratic leadership team and the House Judiciary Committee, drew a red line for the administration. He tweeted Monday that if former White House counsel Don McGahn did not testify before Congress on Tuesday, impeachment proceedings should begin. McGahn ignored the subpoena from the House Judiciary Committee after the White House on Monday presented a legal opinion from the Justice Department asserting McGahn could not be compelled to testify.

Freshman Rep. Alexandria Ocasio-Cortez also tweeted Tuesday that "failure to impeach now is neglect of due process."

And Rep. Justin Amash, R-Mich., recently began the first -- and thus far only -- congressional Republican to call for Trump's impeachment.

Pelosi has said that there will be political retribution from Trump supporters in the upcoming 2020 elections if proceedings begin — something O'Rourke said Tuesday he was willing to risk.

"I understand the political implications of this, but I think this moment calls for us to look beyond the politics and the polling, and even the next election," he said. "It's the very sanctity of the ballot box and the very future of the world's greatest democracy."

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When asked by CNN moderator Dana Bash if he would bear the "short term pain" if he was the Democratic nominee, O' Rourke said: "That's possible."

"The consequence of the alternative is to turn a blind eye to this, and in doing so, is to turn our back on the future of this country, and I cannot be part of that," he said.

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