They came in their thousands, wearing hats, waving flags and exulting in the death of American women’s constitutional right to abortion. But some who marched in Washington on Friday were also thinking ahead: who will be their next champion in the White House?

“If it wasn’t for President Trump, we wouldn’t have a post-Roe America,” said Patricia Stephanoff, 66, from Michigan, wearing a pink “Trump 2024” hat. “He’s the most pro-life president we’ve ever had. He’s the only president who has ever come to the march.”

Not everyone on the first March for Life since the supreme court’s June 2022 decision to overturn Roe v Wade saw it the same way, however. Yvette Griego, from New Mexico, said she preferred Trump’s former vice-president, Mike Pence, because he stood for his convictions and beliefs.

Abortion is emerging as one of the first animating issues and key point of differentiation in the nascent Republican presidential primary for 2024, with Trump, the one officially declared candidate, and various likely rivals already jostling for position.

Each faces a tightrope as they must demonstrate their hardline anti-abortion credentials to the base voters that dominate a Republican primary, then manage or mitigate the subject in a way that does not alienate independents and moderates in a general election.

The awkwardness was spelled out in last year’s midterm elections, less than five months after the demise of Roe v Wade allowed states to enact near or total bans on abortion. Numerous Republican candidates stressed their opposition to reproductive rights during the primaries, only to then scrub such language from their campaign websites when they faced Democrats.

Voters were not fooled and Republicans underperformed, losing a seat in the Senate and gaining only a 10-seat majority in the House of Representatives. Anti-abortion extremists such as Tudor Dixon in Michigan, Adam Laxalt in Nevada and Doug Mastriano in Pennsylvania crashed and burned.

An analysis by the the Henry J Kaiser Family Foundation found that nearly half of voters said the supreme court’s decision to overturn Roe v Wade had a major impact on which candidates they supported in this election, with almost two-thirds of those voting for Democratic House candidates.

No one is finding the issue more vexing than Trump himself. Seeking to shift blame for Republicans’ poor showing, he said this month: “It was the ‘abortion issue’, poorly handled by many Republicans, especially those that firmly insisted on no exceptions, even in the case of rape, incest, or life of the mother, that lost large numbers of voters.”

The observation drew criticism from Christian evangelical leaders who have so far been slow to endorse Trump’s 2024 bid, perhaps aware that others may outflank him on the right. So it was no surprise this week when Trump sought to shore up his anti-abortion credentials, reminding conservatives that he was the one who tilted the balance of the supreme court.

In an interview on Real America’s Voice on Monday, he said: “Nobody has ever done more for right to life than Donald Trump. I put three supreme court justices, who all voted, and they got something that they’ve been fighting for 64 years, for many, many years.”

Not for the first time, Trump seems to have few genuine ideological beliefs. In his days as a New York property developer and celebrity, he said he was pro-choice. But during his 2016 election, he declared “there has to be some form of punishment” for women who have abortions.

Stuart Stevens, a co-founder of the Lincoln Project, an anti-Trump group, said: “Trump has been all over the place on abortion. He’s had more positions than George Santos has names. He was adamantly pro-choice at one time before he ran for president.”

Pence, whose recently published memoir is titled So Help Me God, is a more convincing zealot. He has endorsed a national 15-week abortion ban proposed last year by Senator Lindsey Graham of South Carolina. His uncompromising stance could be a unique selling point in states such as Iowa in the Republican primaries – and a serious liability in the general election.

The former vice-president told the Daily Signal this week that he “strongly” disagrees with Trump’s comments about the midterms, contending that candidates with a “clear, unambiguous commitment to life” performed well.

Pence’s non-profit organisation, Advancing American Freedom, has proposed a law that would extend protections to embryos by declaring that life begins at the moment an egg is fertilised and a law that could open the way to banning Plan B emergency contraceptives and some forms of birth control.

The Democratic National Committee said in a press release: “Pence has made his anti-abortion stances the hallmark of his shadow campaign for the 2024 Republican primary – drawing his fellow GOP contenders to showcase their extremism as well as they each compete for the Maga base.”

Among them is Ron DeSantis, the governor of Florida currently leading Trump in some polls, who in April signed a bill banning abortions after 15 weeks of pregnancy with no exceptions for rape or incest.

That did not go far enough for Kristi Noem, the governor of South Dakota. Her spokesperson, Ian Fury, told the conservative National Review magazine: “Governor Noem was the only governor in America on national television defending the Dobbs decision [that overturned Roe v Wade]. Where was Governor DeSantis? Hiding behind a 15-week ban. Does he believe that 14-week-old babies don’t have a right to live?”

The surprise attack might reflect Noem’s presidential ambitions – or an effort to catch the eye and curry favour with Trump as a possible pick for running mate. Meanwhile Glenn Youngkin, the governor of Virginia and another potential candidate, has thrown his weight behind a 15-week ban in the state with exceptions for rape, incest and the life of the mother.

And Mike Pompeo, a former secretary of state, has promoted his work in the Trump administration reimplementing and expanding the “Mexico City policy” – a ban on US foreign aid for overseas groups that make referrals for abortions or give patients information about the procedure. He tweeted last year: “Now, with Roe overturned, we will see which politicians supported the pro-life cause to win elections, and which actually believed it.”

Each is eager to impress anti-abortion groups likely to carry huge sway in the Republican primary. On a call with reporters this week, Marjorie Dannenfelser, president of the Susan B Anthony List, said any Republican hopeful who shied away from pushing for new federal restrictions on abortion had “disqualified him or herself as a presidential candidate in our eyes and, having done so, has very little chance of winning the nomination”.

Dannenfelser said she and her team would meet potential nominees in the coming months. She held talks recently with DeSantis and was “extremely satisfied” by his commitment to advancing anti-abortion legislation in the state. She said he had described the state’s ban on abortion after 15 weeks as a “start” but added that the governor did not know yet what his next steps on abortion would be.

Above all, Dannenfelser warned candidates not to adopt the “ostrich strategy”, which she described as a misguided – and electorally costly – effort by some Republicans to avoid discussing their position on abortion. In 2022, candidates who embraced the approach out of fear of alienating key voters fared poorly, she argued, compared with those who aggressively defended their anti-abortion positions, such as DeSantis and the Florida senator Marco Rubio.

“I would say if you could only give one lesson learned it would be the result of the ostrich strategy is disastrous for candidates,” she told reporters. “If that’s what happens in the coming federal elections, we will see the same result.”

Despite last summer’s triumph, the base remains hungry for more. Last week the Republican-controlled House passed a resolution to condemn attacks on anti-abortion facilities, including crisis pregnancy centers, and a separate bill that would impose new penalties if a doctor refused to care for an infant born alive after an abortion attempt. Neither is expected to pass the Democratic-led Senate.

But last August voters in deep red Kansas delivered a warning to Republicans, decisively voting to continue to protect abortion rights in the state constitution. Then came the letdown of the midterms. The issue could trouble Republicans again in House, Senate and governors’ races next year.

Wendy Schiller, a political science professor at Brown University in Providence, Rhode Island, said: “Abortion is most likely the No 1 internal problem for the Republican party going into ’24. Independents went by somewhere around 3% for Democrats and most of them, women anyway, went because of abortion.

“If you adopt a strident, complete ban on abortion, I just don’t see how you win nationally. You can’t win Michigan. You can’t win Pennsylvania. You do the electoral college map and I wonder how the Republicans see a road to the White House if they adopt a complete ban on abortion.”

Yet the likely candidates in what could be an ugly Republican primary are trying to outdo each other in attacking reproductive rights and throwing red meat to the base. Christina Reynolds, a spokesperson for Emily’s List, which works to help elect Democratic female candidates in favour of abortion rights, said: “They don’t just have a messaging problem; they have a policy problem.

“Republicans are already in a race to the bottom: how quickly and how drastically can we take away people’s rights? They are misreading what the voters want. Voters have told them very clearly. That may play in parts of a Republican primary but it won’t work for them in the end.”