Criminal charges? Trump is under DOJ investigation for 2020 election.

Former President Donald Trump said Tuesday he has received a letter informing him that he is a target of the Justice Department’s investigation into efforts to overturn the results of the 2020 presidential election, an indication he could soon be charged by U.S. prosecutors.

New federal charges, on top of existing state and federal counts in New York and Florida and a separate election-interference investigation nearing conclusion in Georgia, would add to the list of legal problems for Mr. Trump as he pursues the 2024 Republican presidential nomination.

Mr. Trump disclosed the existence of a target letter in a post on his Truth Social platform, saying he received it Sunday night and he anticipates being indicted. Such a letter often precedes an indictment and is used to advise individuals under investigation that prosecutors have gathered evidence linking them to a crime. Mr. Trump himself received one soon before being charged last month in a separate investigation into the illegal retention of classified documents.

A spokesman for special counsel Jack Smith, whose office is leading the investigation, declined to comment.

Legal experts have said potential charges could include conspiracy to defraud the United States and obstruction of an official proceeding, in this case, Congress’ certification of President Joe Biden’s electoral victory.

Mr. Smith’s team has cast a broad net in its investigation into attempts by Mr. Trump and his allies to block the transfer of power to Mr. Biden in the days leading up to the Jan. 6 riot at the U.S. Capitol, when Trump loyalists stormed the building in a bid to disrupt the certification of state electoral votes in Congress. More than 1,000 people accused of participating in the riot have been charged.

Mr. Smith’s probe has centered on a broad range of efforts by Mr. Trump and allies to keep him in office, including the role played by lawyers in pressing for the overturning of results as well as plans for slates of fake electors in multiple battleground states won by Mr. Biden to submit false electoral certificates to Congress.

Prosecutors have questioned multiple Trump administration officials before a grand jury in Washington, including former Vice President Mike Pence, who was repeatedly pressured by Mr. Trump to ignore his constitutional duty and block the counting in Congress of electoral votes on Jan. 6.

They’ve also interviewed other Trump advisers, including former Trump lawyer Rudy Giuliani, as well as local election officials in states including Michigan and New Mexico who were targets of a pressure campaign from the then-president to overturn election results in their states. A lawyer for Mr. Giuliani, who participated in a voluntary interview, said Tuesday that he did not receive a target letter.

In a related case, Michigan’s attorney general filed felony charges Tuesday against 16 Republicans who acted as fake electors for Mr. Trump in 2020. They were accused of submitting false certificates confirming they were legitimate electors despite Mr. Biden’s victory in the state.

Mr. Trump has consistently denied wrongdoing and did so again in his Tuesday post, writing, “Under the United States Constitution, I have the right to protest an Election that I am fully convinced was Rigged and Stolen, just as the Democrats have done against me in 2016, and many others have done over the ages.”

Mr. Trump remains the Republican party’s dominant frontrunner in the 2024 presidential race, despite indictments in New York and in Florida, which appear to have had little impact on his standing in the crowded GOP field. The indictments also have helped his campaign raise millions of dollars from supporters, though he raised less after the second than the first, raising questions about whether subsequent charges will have the same impact.

A fundraising committee backing Mr. Trump’s candidacy began soliciting contributions just hours after he revealed the new letter, casting the investigation as “just another vicious act of Election Interference on behalf of the Deep State to try and stop the Silent Majority from having a voice in your own country.”

Meanwhile, Mr. Trump continued to campaign as usual. He traveled Tuesday to Iowa, where he criticized investigators and tried to make light of his mounting legal woes as he spoke at a local GOP meeting and taped a town hall with Fox News host Sean Hannity.

The Trump indictments have proven politically challenging for some of Mr. Trump’s rivals, who must be mindful of his deep support among many of the party’s primary voters as well as their distrust of federal law enforcement.

Asked about the letter during a press conference in South Carolina, Florida Gov. Ron DeSantis, Mr. Trump’s most serious challenger, said he hadn’t seen it, but delivered his most forceful critique to date of Mr. Trump’s inaction on Jan. 6.

“I think it was shown how he was in the White House and didn’t do anything while things were going on. He should have come out more forcefully,” Mr. DeSantis said. However, he added, “But to try to criminalize that, that’s a different issue entirely.”

House Speaker Kevin McCarthy, who had previously criticized Mr. Trump for his actions that day, accused Democrats of trying to “weaponize government to go after their number one opponent.”

Mr. Trump, since leaving office, has increasingly downplayed the events of Jan. 6, describing the rally he held that day as a “lovefest” and “a beautiful thing.” He has also embraced defendants jailed for their alleged roles in the insurrection, including promising to pardon a “large portion” and to issue an official apology to them if he is reelected.

In June, he spoke at a fundraiser for the defendants and earlier this year collaborated on a song called “Justice for All,” a version of the Star-Spangled Banner sung by a choir of Jan. 6 defendants and recorded over a prison phone line that is overlaid with Mr. Trump reciting the Pledge of Allegiance.

Some Trump campaign officials and allies argue the country has largely moved on from Jan. 6 and see the latest investigation as similar to others, believing it will have little impact.

One purpose of a target letter is to advise a potential defendant that he or she has a right to appear before the grand jury. Mr. Trump said in his post that he has been given “a very short 4 days to report to the Grand Jury, which almost always means an Arrest and indictment.” Aides did not immediately respond to questions seeking further information.

Prosecutors in Georgia are conducting a separate investigation into efforts by Mr. Trump to reverse his election loss in that state, with the top prosecutor in Fulton County signaling that she expects to announce charging decisions next month.

In his post on Tuesday, Mr. Trump wrote that “they have now effectively indicted me three times ... with a probably fourth coming from Atlanta.” He added in capital letters, “This witch hunt is all about election interference and a complete and total political weaponization of law enforcement.”

Mr. Trump was indicted last month on 37 federal felony counts in relation to accusations of illegally retaining hundreds of classified documents at his Florida estate, Mar-a-Lago. He has pleaded not guilty. A pretrial conference, in that case, was held Tuesday in Fort Pierce, Florida, where a judge said she expected to soon decide on a trial date.

This story was reported by The Associated Press. AP writers Jill Colvin in New York and Alanna Durkin Richer in Boston contributed to this report.