Democratic presidential hopeful Steve Bullock Steve BullockMcConnell locks down key GOP votes in Supreme Court fight Senate Democrats demand White House fire controversial head of public lands agency Pence seeks to boost Daines in critical Montana Senate race MORE warned Wednesday that intraparty rifts within the crowded primary field threaten to undermine the party’s larger ambitions of defeating President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE in 2020.

Speaking at the National Press Club in Washington, D.C., the Montana governor recalled the explosive clashes between centrists and progressives that erupted during the second round of Democratic primary debates in Detroit last week.

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“As I stood on that debate stage last week and then listened to that next night, I saw [Trump’s] reelection becoming more likely with each passing minute,” Bullock said.

“Let me put it plainly: We cannot defeat Donald Trump’s politics of personal destruction if we practice the politics of self-destruction,” he added. “The fact is, we are well on our way to losing this election long before it ever really even is started.”

Tensions between competing factions of the Democratic Party have simmered in the presidential primary field for months. But they burst into public view last week as the candidates argued over their views on health care, immigration and criminal justice reform.

The debate also saw some candidates turn on the legacy of former President Obama, one of the Democratic Party’s most popular figures.

New York City Mayor Bill De Blasio (D), for instance, repeatedly pressed former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE on what he did to curb immigrant deportations during the Obama administration. And Julián Castro, the Housing and Urban Development secretary under Obama, suggested that Biden had failed to acknowledge the shortcomings of the administration in which he served.

“It looks like one of us has learned the lessons of the past and one of us hasn't," Castro said, addressing Biden.

Trump himself addressed the intraparty clashes that broke out during the debates.

"The Democrats spent more time attacking Barack Obama Barack Hussein ObamaObama warns of a 'decade of unfair, partisan gerrymandering' in call to look at down-ballot races Quinnipiac polls show Trump leading Biden in Texas, deadlocked race in Ohio Poll: Trump opens up 6-point lead over Biden in Iowa MORE than they did attacking me, practically," Trump told supporters at a rally in Cincinnati on Thursday.

Bullock, who has polled near the bottom of the pack of two dozen Democratic candidates, made his inaugural appearance in the presidential debates last week after he failed to qualify for the first round of primary debates in late June. He was the first to speak during the debates in Detroit and knocked "wish list economics" from progressives.