House Speaker Nancy Pelosi on Tuesday doubled down on the need to pass the For the People Act despite the election overhaul legislation suffering a big setback over the weekend with moderate Democrat Sen. Joe Manchin vowing to oppose the bill.

Pelosi said there's an "urgent" need to pass the election legislation, known as H.R. 1 in the House and S. 1 in the Senate, because of voter suppression efforts by the GOP at the state level. 

"We are at [an] urgent moment because of the Republican assault on our Democracy," Pelosi said Tuesday in a letter to her Democratic colleagues. "By contrast, Congressional Democrats have brilliantly and patriotically proposed legislation to respect the sanctity of our Democracy."

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Manchin, D-W.Va., on Sunday announced his opposition to the legislation saying it's too partisan and would further divide the country – a move that essentially sinks the legislation from any chance at passage in the Senate. In an op-ed expressing his opposition to the election reform bill, Manchin urged the Senate to pass the John Lewis Voting Rights Advancement Act, named for the late congressman and civil-rights leader. 

But Pelosi said Tuesday that the John Lewis legislation won't be ready until fall and it's "no substitute" for the H.R. 1 legislation that already passed the House.

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"It is essential that H.R. 4, the John Lewis Voting Rights Advancement Act, become law," Pelosi, D-Calif., said. "When we pass H.R. 4, we must do so in a way that is ironclad constitutionally.  This is what Congressman Butterfield and the House Judiciary Committee are hard at work on now. H.R. 4 must be passed, but it will not be ready until the fall, and it is not a substitute for H.R. 1.  Congressman John Lewis wrote 300 pages of H.R. 1 to end voter suppression.  H.R. 1/S. 1 must be passed now. "

Pelosi also expressed frustration that the Senate failed to pass legislation to form an independent commission to investigate the Jan. 6 attack on the Capitol. Senate Republicans filibustered the legislation that already passed the House with the support of 35 Republicans. Pelosi said she hoped the Senate will try again for passage, but if not she signaled House Democrats were prepared to go forward with their own investigation. 

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"We are still hoping the Senate will pass the January 6th Commission," Pelosi wrote. "If not, we will be prepared to seek and find the truth of the assault on the Capitol, our Congress and our Democracy."