Top Democrats have made a last-minute pitch to Republicans as to why they should put partisanship aside and vote to impeach US President Donald Trump.
Mr Trump is expected to become the third US president to be impeached when the full Democratic-led House of Representatives votes on the charges, likely this week.
If the House votes in favour of the charges it will set up a trial in the Republican-controlled US Senate.
House Intelligence Committee Chairman Adam Schiff warned Trump poses "a clear and present danger" to democracy.
Mr Schiff and House Judiciary Committee Chairman Jerrold Nadler said lawmakers have a constitutional duty to hold Trump to account for trying to recruit Ukraine to launch a corruption investigation into his Democratic political rival Joe Biden.
Chairman of the House Permanent Select Committee on Intelligence Adam Schiff (c). Source: AAP
Their comments on ABC's This Week program come as the House is poised later this week to vote along party lines on whether to approve two articles of impeachment.
The Republican-controlled Senate has shown little appetite for removing Trump from office.
"The misconduct hasn't stopped," Mr Schiff said, noting that Mr Trump has still urged Ukraine, as well as China, to investigate the Biden family.
Mr Trump's personal lawyer Rudy Giuliani is still traveling to Ukraine to conduct a "sham" investigation, Mr Schiff added.
"The threat to our election integrity ... goes on. It's a clear and present danger, I think, to our democracy and not something that we can turn away from simply because the Republicans in the House refuse to do their duty."
Both Democrats used their air time on Sunday to urge the Senate to call witnesses and seek documentary evidence they said the White House has withheld.
Senate Majority Leader Mitch McConnell has raised the prospect of conducting a short Senate impeachment trial without calling any witnesses.
Mr Nadler on Sunday said such a move would do a disservice to the Senate, whose members will all effectively serve as jurors who will need to weigh the evidence to decide whether Mr Trump should be convicted and removed from office.
"I think the record is overwhelming, but if they don't think there is sufficient evidence on the record, they should demand the testimony of people ... like Secretary of State Pompeo, and Mulvaney, and others - John Bolton- who on the president's instructions have refused to testify," Mr Nadler said.
Some of Mr Trump's staunch Republican defenders in the Senate have already said they believe Mr Trump did nothing wrong, though others have taken a more cautious approach, saying they want to see the evidence first.
"I think we ought to hear what the House impeachment managers have to say, give the president's attorneys an opportunity to make their defence, and then make a decision about whether and to what extent we go forward from there," Republican Senator Pat Toomey said on NBC's Meet the Press on Sunday.
He added it would be "extremely inappropriate to put a bullet in this thing immediately" when the House votes to impeach Trump and kicks it over to the Senate for trial.
