Former President Donald Trump can still be elected president -- even if he is convicted -- experts tell ABC News. But there are practical reasons that could make it a challenge, experts say.

Trump said recently at the annual Conservative Political Action Conference that he would "absolutely" stay in the race for president even if he were to be criminally indicted.

Trump has denied wrongdoing and has characterized the probe as part of a "witch hunt" against him.

The U.S. Constitution does not list the absence of a criminal record as a qualification for the presidency.

Constitutional experts also told ABC News that previous Supreme Court rulings hold that Congress cannot add qualifications to the office of the president. In addition, a state cannot prohibit indicted or convicted felons from running for federal office.

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-ABC News' Laura Romero

Former President Donald Trump told ABC News over the phone that the indictment is "an attack on our country."

He called it a "political persecution," adding, "They are trying to impact an election."

Trump in a statement Thursday called himself a "completely innocent person" facing "an act of blatant Election Interference."

Trump said, "Our Movement, and our Party - united and strong - will first defeat [Manhattan District Attorney] Alvin Bragg, and then we will defeat Joe Biden, and we are going to throw every last one of these Crooked Democrats out of office so we can MAKE AMERICA GREAT AGAIN!”

Trump's attorneys said in a statement Thursday, "He did not commit any crime. We will vigorously fight this political prosecution in Court."

Trump's son, Donald Trump Jr., said on his podcast Thursday, "This is weaponized justice at its worst."

Stormy Daniels' lawyer, Clark Brewster, issued a statement on the indictment, saying: "The indictment of Donald Trump is no cause for joy. The hard work and conscientiousness of the grand jurors must be respected. Now let truth and justice prevail. No one is above the law."

While the indictment remains under seal, Trump had been under investigation by the Manhattan district attorney over a $130,000 payment he made to the adult film actress to keep her from going public with a claim of an affair, which he denies.

Donald Trump being formally accused of a crime could change the outlook for the still-forming field of Republican presidential candidates in 2024 -- either rallying primary voters primed by his talk of the "deep state" and "retribution" or opening up an unprecedented line of criticism for Trump's rivals.

The indictment itself isn't disqualifying, legally speaking. The U.S. Constitution doesn't prevent people under indictment or criminal investigation from running for the White House, experts have told ABC News, so the former president could still be reelected despite the indictment -- and would still be eligible even if it leads to a conviction, regardless of practical obstacles like potential incarceration.

A white powder was discovered in the mailroom at 80 Centre Street, where the Manhattan District Attorney has offices and where a grand jury has been meeting to hear evidence in former President Donald Trump's case, according to a court official. The powder was determined to be non-hazardous, officials said.

The powder came in an envelope addressed to "Alvin," an apparent reference to Manhattan District Attorney Alvin Bragg, according police sources.

Inside the envelope was a letter containing the typewritten message, “Alvin: I am going to kill you," with 13 exclamation points, according to sources.

This envelope followed a series of unfounded threats that targeted municipal offices in New York this week.

"For three days we got four emails," Susan Stetzer, district manager at Manhattan Community Board 3, told ABC News on Friday.

At least one of the messages prompted the court to pause a hearing in the New York Attorney General’s civil lawsuit against Trump.

None of the email messages mentioned Trump by name. One included what Stetzer described as a "horrible homophobic rant."

According to Stetzer, the messages came from @mail.ru domains and some contained Cyrillic characters. The FBI is aware but does not immediately assess that the emails came from Russia, according to a law enforcement official.

"We did not get one today so I’m hoping it stops," Stetzer said.

New York City courthouses will see increased security, the Office of Court Administration said Friday.