Transcript for Postmaster general to testify before Congress amid controversial USPS changes
Monday night, and as the convention gets under way, so many questions about the U.S. Postal service. Tonight, the president is now denying he's trying to slow it down as the election nears. But it's not just mail-in voting, not just the election, it's prescription drugs, it's jobless benefits, it's what small towns and large depend on from the postal service every day in this country. The president says he's not slowing anything down, even as he rails against voting by mail. And he's defending moves by the new postmaster general, a major trump donor, who will now appear before congress next week. And tonight, house speaker Nancy Pelosi is now calling the house back in session. Here's ABC's chief white house correspondent Jonathan Karl. Reporter: Today, Donald Trump insisted he is not trying to undermine the post office to help himself win the election. Have you ever encouraged the postmaster general, a big donor to you, to slow the mail? No, not at all. Wouldn't do that. Reporter: The new postmaster general, a major donor to the president's campaign, has put in place cost-cutting measures that have already reportedly slowed down mail delivery. Democrats call it a deliberate effort to sabotage the expected surge in mail-in voting. Speaker of the house Nancy Pelosi today called the house back into session to deal with the issue, saying, quote, "Lives, livelihoods and the life of our American democracy are under threat from the president." It's not just ballots being affected. Jim Gaul says a reimbursement claim for his wife's medications usually takes six days but recently took weeks. We have to pay for her prescriptions and then file for reimbursement. $12,000 is a lot of money to have outstanding on a credit card. Reporter: The president has said he opposes a democratic proposal for $25 billion in additional funding to the postal service, but has acknowledged that without more money, they will not be able to deal with the surge in mail-in voting. Though he votes by mail himself, the president claims, without evidence, that expanding mail-in voting will lead to massive vote fraud. With respect to universal mail-in voting, it's just like a total catastrophe what's happening. Reporter: But senate Republican leader Mitch Mcconnell disagrees. I don't share the president's concerns. Reporter: In the face of bipartisan criticism, the president now says he is open to additional funding for the post office. We'll take care of the post office. Reporter: As Democrats accuse the president of abusing the post office for political gain, a former top trump administration official says the president repeatedly did the same thing with the department of homeland security. What we saw week in and week out, and for more, after two and a half years in that administration, was terrifying. Reporter: Miles Taylor served as the chief of staff at dhs and says the president repeatedly exploited the department to serve his own political agenda, even trying to cut funding to deal with wildfires in California, because the state is run by Democrats. He told us to stop giving money to people whose houses had burned down from a wildfire, because he was so rageful that people in the state of California didn't support him and that politically it wasn't a base for him. Reporter: Taylor, a lifelong Republican, says he is voting for Joe Biden. So, let's get right to Jon Karl, with us live as well tonight. And Jon, you reported there on the former official at the department of homeland security making news today, but I do want to get back to the postal the Democrats, you reported there, have called the postmaster general to testify before congress next week and tonight he says he'll be there? Reporter: The postmaster general says he will be there and apparently the president is not happy about that. In a tweet just a short while ago, he asked why Democrats have scheduled the hearing for next week during the Republican virtual convention, saying, quote, "They are always playing games," the president tweeted "Get tough Republicans." David? Jon Karl, we'll see you later tonight, as well. Thank you, Jon.
This transcript has been automatically generated and may not be 100% accurate.