By Tim Reid and Alexandra Ulmer

Republican presidential rivals Donald Trump and Ron DeSantis appeared at the same event in the 2024 White House race for the first time on Friday, but even a day after Trump faced fresh criminal charges, it was the former president talking down DeSantis rather than the other way around.

Trump, who has all year relentlessly attacked DeSantis, his nearest rival for the Republican nomination, told a crowd of Iowa Republicans "not to take a chance" on the Florida governor he mockingly calls "DeSanctus", among other nicknames.

DeSantis was seen as a major threat to Trump at the beginning of the year but his campaign has been flagging in recent weeks.

He declined to go after Trump at the Republican Lincoln Day dinner in Des Moines, where the two men and 11 other Republican White House hopefuls were given 10 minutes each in front of 1,200 attendees.

Only one Republican candidate - Will Hurd, a former Texas congressman and a longshot, went after Trump - and he was booed after he said: "Donald Trump is running to stay out of prison".

Trump has been indicted twice this year, and his poll numbers in the Republican presidential nomination race keep going up.

In March, he was charged in New York over falsifying business records over an alleged hush money payment to a porn star, which Trump has pleaded not guilty to.

In June, Trump faced yet more charges when special counsel Jack Smith unveiled a 37-count indictment accusing him of willful retention and improper sharing of national defense information.

Thursday's fresh charges were related to that case, when Trump was charged with ordering a member of staff at his Florida home to delete security videos to thwart an FBI investigation, among three new criminal counts against Trump, bringing the total to 40.

Still, Trump dominates the Republican field, and his lead has grown stronger since the criminal charges. It plays into his central argument that he is a victim of a runaway Justice Department.

The problem for DeSantis and his other rivals is they have not yet worked out a way to counter a frontrunner who is facing multiple criminal charges. DeSantis has shied away from attacking Trump over the indictments, out of fear of alienating the Republican base.

But if the Florida governor does not work out a way to take on Trump directly, pollsters say he and the others are running out of time to stop Trump becoming the nominee.

Trump's lead over DeSantis, who has been slipping in the polls, is roughly 30%, while none of the other Republican hopefuls have broken out of single digits, according to polls.

(Reporting by Tim Reid and Alexandra Ulmer; Editing by Lincoln Feast.)