Donald Trump, reeling from another electoral setback, is facing pressure to delay his announcement of a new bid for the White House until after a crucial Senate race next month.

Trump-endorsed candidates slumped to defeat in Tuesday’s midterm elections, leaving the former president at arguably his weakest standing in the party since the riot at the US Capitol last year.

Trump looks set to announce a third consecutive run for president next Tuesday but some in his inner circle are cautioning him to wait until after the Senate runoff in Georgia on 6 December.

Trump-backed Herschel Walker and the Democratic incumbent, Raphael Warnock, will face off after neither passed 50% of the vote on Tuesday. The race could decide control of the Senate, depending on results in Arizona and Nevada.

Jason Miller, a senior Trump adviser, told the rightwing network Newsmax: “Everything comes down to Herschel Walker and Georgia. And if we can pull that off, we might get … Chuck Schumer packing from the [Senate] majority leader’s office.

“I’m advising the president to hold off until after the Georgia race, after Herschel Walker … This is bigger than anything else in the country.”

Miller also said Trump should deploy campaign funds to help Walker, a controversial former football star.

Republicans had expected widespread success in the midterms but though the House looked set to change hands, the Senate remained on a knife-edge after a high-profile Trump-endorsed candidate, the TV doctor Mehmet Oz, fell to embarrassing defeat in Pennsylvania. Many are pointing the finger at Trump.

Tara Setmayer, a senior adviser to the anti-Trump group the Lincoln Project, said: “He is wounded and that’s evidenced by the rightwing media ecosystem putting out collective rebukes in the wake of a disappointing midterm result because Donald Trump was at the centre once again.

“He cost them a much larger victory in the midterms. He is the albatross around the Republican party’s electoral neck and will continue to be as long as he is alive and breathing.”

Trump is holding an event at his Mar-a-Lago estate in Florida next week where he is expected to announce his run. He has taken shots at Ron DeSantis, the Florida governor widely seen as his chief rival. But DeSantis enjoyed a strong night on Tuesday, winning a landslide, his victory speech greeted by chants of “two more years”. Worryingly for Trump, allies including the Rupert Murdoch-owned New York Post have come out strongly for DeSantis.

A column on the Fox News website proclaimed: “Ron DeSantis is the new Republican party leader. Republicans are ready to move on without Donald Trump.”

But Setmayer, a former Republican communications director on Capitol Hill, cautioned: “I’m not holding my breath that this posture will remain. We saw this before after the election in 2020 and it lasted as long as the ratings started to crash.

“When they started losing ratings to Newsmax and other media outlets, they went right back to the fawning coverage of Donald Trump. Are they willing to remain steadfast this time around because they think now that Ron DeSantis is the heir apparent? We’ll see how long that lasts.”

On Wednesday, Fox News reported that Trump would not delay his announcement. On Thursday, Trump launched a tirade on his Truth Social platform.

“For those many people that are being fed the fake narrative from the corrupt media that I am angry about the midterms, don’t believe it,” he wrote. “I am not at all angry, did a great job (I wasn’t the one running!), and am very busy looking into the future. Remember, I am a ‘Stable Genius’.”

Trump also criticised reports that he blamed his wife, Melania, and friend, Fox News host Sean Hannity, for talking him into backing Oz in Pennsylvania.

“I’d like to apologise to Melania and Sean Hannity for all of the Fake News and fictional stories (made up out of thin air, with no sources despite them claiming there are!)” wrote Trump, whose attacks on the media often prove unfounded.

It is not a foregone conclusion that Trump will express robust support for Walker. Trump has attacked Mitch McConnell, the Republican Senate leader. He is also widely held to have contributed to the loss of the Senate in 2021. Then, Warnock and Jon Ossoff won Georgia runoffs as Trump persisted in his lie that his defeat by Joe Biden was the result of electoral fraud, potentially depressing Republican turnout.

Nationally, Republican hand-wringing continued. Chris Christie, a former New Jersey governor and a longtime Trump ally, told the Associated Press: “We lost in ’18. We lost in ’20. We lost in ’21 in Georgia. And now in ’22 we’re going to net lose governorships, we’re not going to pick up the number of seats in the House that we thought and we may not win the Senate despite a president who has a 40% job approval.

“There’s only one person to blame for that and that’s Donald Trump … The only animating factor in determining an endorsement is, ‘Do you believe the 2020 election was stolen or don’t you?’”

The Republican strategist David Urban, a former Trump adviser, told the AP: “How do people feel in America? I think people feel not great about the Trump brand right now. It’s bad.”

Commentators, however, noted that Trump has been written off before but still holds sway over the Republican base, as evidenced by rallies that draw fiercely loyal crowds.

Joe Walsh, a podcast host and former Republican congressman from Illinois, said: “We’ve seen this movie before. He led a fucking insurrection and the party still bowed to him. So will the dam finally break with this one? No, I don’t think it will. I still think it’s his party.

“This whole DeSantis thing is overrated. Trump knows that … I still expect him to come out this month and announce he’s running and I don’t expect many Republicans to have the balls to say, ‘Donald, you suck.’”