LAS VEGAS — Trying to quell accusations that he is ousting activists from the party's left flank, Democratic Chairman Tom Perez told fellow Democrats on Saturday that unity is crucial in the fight against President Donald Trump, whom he lambasted as an "existential threat" to the nation.

"We have the most dangerous president in American history and one of the most reactionary Congresses in American history," Perez said as he addressed the first Democratic National Committee gathering since his February election.

The former Obama Cabinet official blistered "a culture of corruption" that he said extends to Trump's Cabinet, House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell, but he warned that internal ruckuses over party priorities and leadership would distract from the goal of winning more elections to upend Republicans' domination in Washington.

The chairman's plea comes amid a rift over his appointments to little-known but influential party committees and the 75 at-large members of the national party committee. Perez and his aides plug his choices as a way to make the DNC younger and more diverse, but the moves also mean demotions for several prominent Democrats who backed Bernie Sanders over Hillary Clinton in the 2016 presidential primaries and then supported Minnesota Rep. Keith Ellison over Perez in the postelection race for party chairman.

Perez spent time during this week's proceedings meeting privately with frustrated DNC members, including some he did not reappoint. He apologized publicly Saturday for not reaching all of those members before he announced his appointments, but he defended his overall aim.

"If someone ever asks you which wing of the party you belong to, tell 'em you belong to the accomplishment wing of the Democratic Party," he said, "because you're trying to get s