"I don't know that this many months out from the caucuses in Iowa, that these polls really indicate what our prospects are," the former Texas congressman told ABC News Chief Anchor George Stephanopoulos. "If I relied on polls, in any race that I'd run, I never would have been able to serve in the United States Congress, we never would have tried to take on Ted Cruz, we never would have been able to lead the largest grassroots effort in the history of the state of Texas."
O'Rourke, who represented the border city of El Paso, Texas for three terms in Congress, also gave his rationale as to why he believes he is the best candidate to take on President Donald Trump, pointing to the counter-rally he spoke at during the president's visit back in February, and his ability to win Independents and Republicans.
"I went to each one of the 254 counties of Texas, won more votes than any Democrat has ever won. Won independents for the first time in decades, and brought along half a million Republicans as well," O'Rourke said. "Frankly, George, the fact that we can bring Texas and its 38 electoral votes with us, shows that we are best prepared to take on Donald Trump to defeat him in November of 2020.
The Texan was also asked about Trump's recently announced deal on new immigration enforcement with Mexico, an achievement that he says is "overblown" and said the process through which it was agreed to could have damaged our relationship with an important ally.
"I think the president has completely overblown what he purports to have achieved. These are agreements that Mexico had already made, in some cases, months ago," O'Rourke said. "They might have accelerated the timetable, but by and large, the president achieved nothing except to jeopardize the most important trading relationship that the United States of America has."
When asked about House Speaker Nancy Pelosi's closed-door comments on Capitol Hill earlier this week -- that she'd rather see Trump go to "prison" than start an impeachment process -- and whether or not Trump has committed prosecutable crimes, O'Rourke said flatly, "he did."
"I think that's clear from what we have learned from the Mueller report, but I think those crimes might extend beyond what we've seen in the Mueller report. The relationship that he has with (Russian President) Vladimir Putin, which has never been properly explained, from the invitation as a candidate to have Russia involve itself in our elections, his efforts to obstruct justice, the fact that he called Vladimir Putin after the Mueller report was released," are all future avenues to investigate, O'Rourke said.
"If we do not hold the president accountable, we will have set the precedent that some people in this country because of their position of power, are in fact, above the law. ... So regardless of the popularity of the idea, or what the polling shows us, we must proceed with impeachment so that we get the facts and the truth," O'Rourke added.
Responding to criticism that he has changed his positions on various issues to keep himself aligned with the shifting dynamics in the Democratic Party, O'Rourke defended his record, saying, "I've always done what is right, not necessarily what is politically popular," and pointing to his support for LGBTQ rights and the legalization of marijuana during his time on the El Paso City Council.
"I am who I am," O'Rourke said. "I'm certainly showing up and listening to people and learning from them in every community. But I'm also showing up with the courage of my convictions, the things that I strongly believe in."
O'Rourke, who rose to national prominence during his U.S. Senate campaign in Texas last year against Republican Sen. Ted Cruz, was in the middle of a four-day swing through the critical early voting state of Iowa.
On Saturday, he joined several of his Democratic rivals at the Capital City Pride festival in Des Moines, Iowa, where he took aim at Trump, who he says is using fear to pit Americans against one another.
"We have this president of the United States, who uses fear to keep us apart, to make us afraid, and to make some of our fellow Americans angry, to prevent us from coming together to make the change that we still need," O'Rourke told a crowd in the shadow of the Iowa State Capitol.
O'Rourke was also asked about the recent controversy in the Democratic primary over abortion that led to a tough week for the race's early frontrunner.
Late Thursday, former Vice President Joe Biden reversed his stance on his support for a measure called the Hyde Amendment that prevents using federal funding for abortion after taking heat from some of his fellow 2020 Democrats.
"For many years as a U.S. senator, I have supported the Hyde Amendment as many, many others have because there was sufficient monies and circumstances where women were able to exercise that right, women of color, poor women, women were not able to have access, and it was not under attack … as it is now. But circumstances have changed," Biden said.
Prior to Biden's reversal, several 2020 challengers criticized him for his support for the amendment, given its impact on low-income and minority women.
"I've always known what I thought on this issue, that every single woman in this country should be able to make her own decisions about her own body," O'Rourke responded Sunday on "This Week."
Stephanopoulos also asked O'Rourke whether there was room in the party for a pro-life Democrat.
"It's very hard for me to believe that we could ever produce a nominee who would not believe in a woman's right to choose," O'Rourke said, "...and the mandate for us to stand with women in each and every instance."
ABC News' Adam Kelsey contributed to this report.