MILWAUKEE —  The Democratic National Committee has delayed plans to virtually nominate President Biden for a possible second term after Senate Majority Leader Chuck Schumer asked for more time amid intensifying Democratic calls for Biden to step aside.

“None of this will be rushed,” DNC rules committee co-chairs Leah Daughtry and Tim Walz, the governor of Minnesota, wrote in a Wednesday letter first reported by CBS News and acquired by The Post.

The letter says “no voting will begin before August 1″ and that “on Friday, we will propose a framework for how to best proceed.”

Schumer has not called on Biden to end his candidacy following his disastrous June 27 debate performance, but met with the president Saturday at the commander in chief’s Rehoboth Beach, Del., vacation home to discuss the election.

A source close to both men said polling numbers were discussed — as down-ballot Democrats expressed alarm that Biden could lose in a landslide to former President Donald Trump and contribute to heavy losses among House and Senate Democrats.

Trump, 78, officially secured the GOP presidential nomination Monday at the Republican National Convention in Milwaukee — after surviving an assassination attempt at a Saturday rally in Pennsylvania.

“Trump is now stronger than ever and down-ballot Dems can only run so far behind a nominee who is losing in every swing state,” a congressional Democratic source told The Post Tuesday.

The delay in nominating Biden — who insists he will continue his campaign for a second term — followed frantic efforts to derail DNC plans to coronate Biden by digital roll call within days.

Before the postponement, a DNC source told The Post that the vote could happen sometime in “mid July,” according to internal discussions among national committee leaders.

It’s not immediately clear when the voting is now expected to begin and end — though balloting spanning several days at least is likely.

Biden said in a BET interview taped Tuesday and released Wednesday that he would consider leaving the race “if I had some medical condition that emerged, if somebody, if doctors came to me and said, you got this problem and that problem.”

A group of House Democrats who want Biden to step aside, citing concerns about his cognitive fitness, drafted and were circulating a letter asking for the delay, Axios reported Tuesday — with the group expressing concern about buzz that voting could begin July 21.

The electronic voting plan was originally devised so that the Democratic ticket would be formalized in time for the Aug. 7 deadline in Ohio for its November ballot.

Dissenters feared that the virtual vote was going to happen early to squelch mounting calls for Biden to step aside following his confused debate performance, which stoked concerns about the mental acuity of the oldest-ever sitting president.

Biden would be 86 if he completes a full second term in January 2029.

Rep. Adam Schiff (D-Calif.) on Wednesday became the 21st House Democrat to call on Biden to stand down, saying that “it is time for him to pass the torch.”

“I think if he is our nominee, I think we lose,” the former chairman of the House intelligence committee and Democratic Senate nominee in California said privately on Saturday, the New York Times reported.

But sources told The Post that Democrats can still pick a new candidate even if Biden is nominated electronically and later decides to retire — including by possibly reopening the process at the Aug. 19-22 Democratic National Convention in Chicago.

“All you do is change the rules on the floor of the convention and allow for additional ballots,” said one DNC source.

Vice President Kamala Harris, 59, is the most likely replacement for Biden atop the Democratic ticket if he decides to leave the race.