More than half of Joe Biden’s supporters are primarily motivated to cast their vote for the president in order to prevent a return of Donald Trump to the White House, according to a new poll.

Opposing Trump is the main reason to back Biden for 54% of the Democratic incumbent’s voters, the new CBS/YouGov poll found, up from 47% in a similar survey conducted in March, which was prior to the presumptive Republican nominee being found guilty of business fraud by a New York jury.

A further 27% of Biden voters are supporting the president because they like him – down from 31% in March – while 19% say that they are backing him because he is the Democratic nominee for president.

The poll comes as the Biden campaign has ramped up its rhetoric in attacking Trump directly in recent weeks, pointing to the former president’s felony conviction and string of past controversies. Last week, Biden said his predecessor is “reckless and dangerous” for complaining that his New York trial was rigged and claimed that he had been driven “crazy” by his 2020 election loss.

The outcome of this year’s presidential election remains in the balance, with the new CBS poll finding Biden and Trump are essentially tied nationally and in key swing states. Trump is on 50% of support among likely voters, and Biden is on 49%, with these figures switched for likely voters in battleground states.

Trump has enjoyed an edge over Biden in most polls taken in recent months, although there is some evidence of a slight shift towards the president in the wake of his predecessor’s felony conviction. Trump, who faces three other felony trials for hoarding classified documents and for trying to subvert the 2020 election, is tentatively scheduled to be sentenced in the New York case on 11 July.

However, the CBS poll found that 55% of likely voters say that Trump’s conviction is not a factor in their choice for president, with 28% saying it will be a major factor. While Trump has enjoyed a fundraising surge from supporters following the trial, the poll found that just 14% of his voters are backing him because of his conviction, with the vast majority saying it isn’t a factor for them.

Eight in 10 Trump voters believe, wrongly, that the former president was charged due to the actions of the Biden administration rather than local prosecutors, the poll found.

Overall, the main motivating issues for voters are the state of the US economy, inflation, the health of democracy and crime, according to the poll.