President Biden said on Tuesday that the fight against restrictive voting laws was the “most significant test of our democracy since the Civil War” and called Donald J. Trump’s efforts to overturn the 2020 election “a big lie.”

In an impassioned speech in Philadelphia, Mr. Biden tried to reinvigorate the stalled Democratic effort to pass federal voting rights legislation and called on Republicans “in Congress and states and cities and counties to stand up, for God’s sake.”

“Help prevent this concerted effort to undermine our election and the sacred right to vote,” the president said in remarks at the National Constitution Center. “Have you no shame?”

But his words collided with reality: Even as Republican-led bills meant to restrict voting access make their way through statehouses across the country, two bills aiming to expand voting rights nationwide are languishing in Congress. And Mr. Biden has bucked increasing pressure from Democrats to support pushing the legislation through the Senate by eliminating the filibuster, no matter the political cost.