Donald Trump does not appear on the ballot paper at the US midterm elections, but the ex-president still looms large.

Rejected by the American public two years, the TV star-turned-politician has been fully embraced by the Republican Party – or at least the Trump playback has become gospel for hundreds of candidates hoping for victory.

Since his fingerprints are everywhere, the elections for the US House of Representatives and the Senate will be interpreted by many as referendum on Trump-ism – and could play a decisive role in whether Trump is the Republican presidential candidate in 2024.

While he is yet say officially, Trump has as near-as-dammit indicated a third presidential run is on.

“I’m going to be making a very big announcement on Tuesday, November 15 at Mar-a-Lago,” Trump said in Ohio on Monday night, where he was holding yet another rally of the midterm season.

Trump explained that he wanted “nothing to detract from the importance of tomorrow”, even after he had sparked a frantic effort to hold him off after he had told people he was considering officially launching his next campaign at the rally.

Trump has been increasingly explicit about his plans to seek another term, saying in recent days that he would “very, very, very probably” run again and would be formalising his intentions “very, very soon”.

“I will probably have to do it again but stay tuned,” he said on Sunday night in Miami. “Stay tuned to tomorrow night in the great state of Ohio.”

The Republicans are expected to do well at the polls for many reasons that have nothing to do with Trump or his positions.

Midterm elections – half-way through the US president’s four-year term in office – typically see the party that holds the White House getting a roasting: see Barack Obama losing the House midway through his first term, and the same happening to Trump in 2018.

Democrats under Joe Biden are also hamstrung by the president’s low approval ratings, fuelled by voter concerns over economy and inflation, even if these have been caused by global factors such as Russia’s invasion of Ukraine.

The Republicans are the favourites to win the House, and they need to pick up just one seat to gain control of the Senate. So given his influence over the slate of candidates put forward by the Republicans, Trump could face being blamed if the elections do not got well (and, by the same token, big victories would be a major fillip for the Trump political brand).

The ex-president has endorsed nearly 300 candidates. Among them is JD Vance, an author, venture capitalist and one-time Trump critic. His decision to back Vance in the state’s hyper-competitive Senate primary vaulted the political newcomer to victory in a crowded Republican field.

Many who back Trump have embraced his American First positions, including his isolationist foreign policy and focus on immigration. In large part they have even taken up his “big lie” about fraud during the presidential vote in 2020. In a case where a GOP nominee has refused to spread the false claim – businessman Joe O’Dea in Colorado – Trump has attacked him, actively hurting both his campaign and Republican chances to win back the chamber.

Commentators point out the grip Trump has on thee party has saddled the GOP with relatively weak candidates in Arizona, Pennsylvania, Georgia and New Hampshire – key states that could decide who holds either chamber.

In Georgia, Trump backed Herschel Walker, a former college football star, which drove away other potential candidates. Walker’s campaign has been dogged by questions about his turbulent personal life, including allegations of domestic violence from his ex-wife and, more recently, two women saying that Walker pressured them to have abortions during their relationships, allegations he has denied. His candidacy could now result in Democratic senator Rafael Warnock holding on to his seat with polls showing a tight race.

Trump is also facing a series of escalating legal challenges, including several investigations that could lead to indictments. They include the probe into hundreds of documents with classified markings that were seized by the FBI from his Mar-a-Lago club in Florida, as well as ongoing state and federal inquiries into his efforts to overturn the results of the 2020 presidential election.

The House committee investigating the January 6, 2021, attack on the US Capitol has also subpoenaed Trump and last month issued a letter to his lawyers saying he must testify, either at the Capitol or by videoconference, “beginning on or about” November 14 and continuing for multiple days if necessary.

And he remains a polarising figure. Trump, who has a history dating back to the 1980s of publicly toying with White House bids only to back down, could also still decide not to run if he fears he could lose either in the Republican primaries or the general election itself. Could his ego take another defeat?

The 2024 campaign will effectively kick off when the polls close on November 8, and potential Republican challengers have spent months carefully laying the groundwork for their own expected campaigns.

Florida governor Ron DeSantis is widely seen as Trump’s most formidable challenger having honed his brand of competent Trump-ism. Former vice president Mike Pence will be releasing a book on the same day as the Trump announcement, which is seen as part of his own potential campaign rollout.

Texas senator Ted Cruz and Florida senator Rick Scott have been aggressively campaigning for midterm candidates, as has former UN ambassador Nikki Haley.