WASHINGTON — President Donald Trump says he'll demand that the Justice Department review whether it or the FBI infiltrated his presidential campaign for political purposes and whether any demands or requests came from the Obama administration.

Trump tweeted Sunday: "I hereby demand, and will do so officially tomorrow, that the Department of Justice look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes – and if any such demands or requests were made by people within the Obama Administration!"

Trump has been promoting a theory circulating in conservative circles about a possible FBI spy on the campaign.

But Trump attorney Rudy Giuliani cast doubt on that last week, saying neither he nor the president knows for certain if there was a spy.

Giuliani says they had been told about possible "infiltration."

At least two Florida lawmakers were vocally supportive of the president's proclamation.

Republican Rep. Matt Gaetz, R-Fort Walton Beach, who's long criticized how law enforcement has handled the investigation into the 2016 Trump campaign's ties to Russia, posted a short tweet about Trump's announcement.

"#BoldLeadership," Gaetz tweeted Sunday.

Rep. Ron DeSantis, R-Palm Coast, whom Trump endorsed in the Florida governor's race, also praised the president on Twitter.

Read more: Florida conservatives to Attorney General: Investigate 'Obama-era' officials

The Justice Department's internal watchdog is already examining Republican complaints of FBI misconduct in the early stages of the Russia investigation.

Inspector General Michael E. Horowitz announced an investigation in March at the request of Attorney General Jeff Sessions and congressional Republicans. Sessions and the lawmakers had urged Horowitz to review whether FBI and Justice Department officials abused their surveillance powers by using information compiled by Christopher Steele, a former British spy, and paid for by Democrats as part of the basis to justify monitoring Carter Page, a former campaign adviser to Trump.

Horowitz said his office will look at those claims as well as communications between Steele and DOJ and FBI officials.

Trump did not elaborate on his "demand," one of a series of tweets he sent throughout the day Sunday. On Saturday, Trump tweeted, "If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal." He said only the release or review of documents the House Intelligence Committee is seeking from the Justice Department "can give conclusive answers."

The Justice Department declined to comment Sunday afternoon on Trump's tweet. The White House didn't immediately respond to a request for comment.

Trump last week accused the Justice Department of trying to frame him by planting a spy in his 2016 campaign. Trump quoted Fox Business anchor David Asman and tweeted Friday: "Apparently the DOJ put a Spy in the Trump Campaign. This has never been done before and by any means necessary, they are out to frame Donald Trump for crimes he didn't commit."

But when asked whether there was an informant on the campaign, Giuliani told CNN, "I don't know for sure, nor does the president, if there really was one," though he said they have long been told there was "some kind of infiltration."

Earlier this month, the National Review raised the question of a possible FBI spy in Trump's campaign. The article cites work by Republican Rep. Devin Nunes of California, an ardent Trump supporter and chairman of the House Intelligence Committee, who has demanded information on an FBI source in the Russia investigation.

Opponents of Nunes' request have stressed the need to protect sources and methods.

The New York Times reported separately last week that at least one government informant met several times with Page and George Papadopoulos, another former foreign policy adviser on Trump's campaign. The Times reported, citing current and former FBI officials, that the informant talked to Page and Papadopoulos because they had suspicious contacts linked to Russia.

Papadopoulos was charged last year in special counsel Robert Mueller's investigation and pleaded guilty to lying to the FBI. He has agreed to cooperate with prosecutors.

Times staff writer Kirby Wilson contributed to this report.