President Trump is launching new attacks on Speaker Nancy Pelosi (D-Calif.), questioning her leadership chops and veering sharply from his previous practice of touting her skills as an accomplished legislator and formidable rival.

The shift arrives as the 2020 Democratic primary is heating up, leaving some observers to speculate that Trump is simply shifting into campaign mode by taking on a Democratic adversary who has long been radioactive in the eyes of conservative voters.

Democrats have struggled, at times, to unite their diverse new majority, and others maintain Trump's strategy is designed to deepen those divisions heading into the 2020 elections.

"It allows the president to emphasize that, I think, there's a lot of confusion when it comes to principles that are governing Democrats," said Mattie Duppler, a Republican strategist.

The shift also comes just days ahead of the expected release of the long-awaited report from special counsel Robert Mueller about Russia's 2016 election interference and whether Trump acted to obstruct that investigation. Trump has denied any wrongdoing throughout the years-long probe, but the intensity and frequency of the denials has only reinforced Democrats' suspicions that he has something to hide - and is using the attacks on Pelosi as a way to shift attention from the investigators' findings.

"The President is interested in changing the subject from the imminent release of the Mueller report," Pelosi spokesman Drew Hammill said Tuesday in an email.

Whatever the reason, the attacks mark a notable shift in Trump's messaging strategy. Over much of his White House tenure, Trump has largely - and curiously - refrained from launching personal attacks against Pelosi, a popular conservative target, reserving his more vitriolic broadsides for her Senate counterpart, Minority Leader Charles Schumer (D-N.Y.).

Following the Democrats' midterm victory, Trump went out of his way to praise Pelosi, saying the pair had a "great relationship" and commending her appeals for bipartisan cooperation on big-ticket legislation like drug pricing and infrastructure.

"I give her a great deal of credit for what she's done and what she's accomplished," he said at the time.

Despite branding many of his opponents with derisive nicknames, the president's alternative title for Pelosi is simply "Nancy," he told reporters in January amid a prolonged partial government shutdown. A short time after that remark, Trump acceded to Pelosi's request to reschedule the State of the Union address until after the government had reopened.

Allies of both camps have said Trump's hands-off approach has been, at least in part, rooted in the president's genuine admiration for the Speaker and the power she bears. Pelosi's opposition to impeaching Trump, while angering some liberals, has also encouraged the president.

"I think when Democrats won the House and Pelosi took the gavel, there was a belief by the president that she would be open-minded towards working across the aisle and getting some things done with him," said a source close to the White House who requested anonymity to speak candidly.

But the sands have shifted over the last week, as Trump has taken new aim at Pelosi amid the conservative outcry over Rep. Ilhan Omar's (D-Minn.) March comments related to the 9/11 terrorist attacks - an episode Trump elevated Friday in a tweet linking Omar to the burning towers of the World Trade Center.

From the left, some liberal outside groups have denounced Pelosi's defense of Omar as too tepid, urging a more aggressive response from the Speaker and her leadership team in condemning the president's attacks on one of the first Muslim women in Congress.

And from the right, Trump has pounced, using the Omar controversy to paint all Democrats as "the radical left" - and to bash Pelosi as an inept leader who's taking her marching orders from the Minnesota freshman.

"[Omar] is out of control, except for her control of Nancy!" Trump tweeted on Monday.

That came just a day after the president had gone after Pelosi for comments she made during a recent sit-down with "60 Minutes" in which she hammered the president as unfit for the office - a segment Trump characterized as a "puff piece."

"[H]er leadership has passed no meaningful Legislation," he tweeted Sunday. "All they do is Investigate, as it turns out, crimes that they instigated & committed."

Pelosi offered a terse, tongue-in-cheek rejoinder: "Thanks for watching!" she tweeted. Yet for the most part, Pelosi has largely ignored the president's social media polemics, focusing instead on Democrats' plans to move on a long list of legislative priorities when Congress returns to Washington later this month following the long spring recess.

"I don't respond to the president's tweets. ... To me it is unpresidential," she said Friday, after Trump had taken to Twitter to hammer Democrats' proposal to raise government spending. "We have serious work to do. What is his purpose in tweeting? I don't know. But our purpose is working together to get the job done for the American people."

The potential implications of the soured Trump-Pelosi relationship are yet unclear. Democrats are expected to move quickly in the coming weeks on legislation to tackle the rising cost of prescription drugs and bolster the nation's infrastructure - two issues where Trump is viewed as a potential ally.

"We haven't taken this to a place that he hasn't professed to have an interest," Pelosi said Friday during the Democrats' annual retreat in the Washington suburbs.

Pelosi said last week that she called Trump and requested a meeting to discuss infrastructure. The two are planning to meet, she told The Associated Press.

Top White House economic adviser Larry Kudlow said Monday that the administration has been in touch with representatives on Capitol Hill about a possible infrastructure package.

"We're looking. We're talking. We'll feel out what's available," Kudlow said on Fox News. "We'd love to do business with the Democratic House, absolutely."

Others are skeptical of a thaw in relations.

The source close to the White House argued that there's no political incentive for Democrats to come to the bargaining table and deliver a win for Trump leading up to the election.

"In the beginning, he saw a pathway toward bipartisanship with Pelosi and didn't want to ruin that by going after her," the source said. "But now that he sees that Pelosi is basically afraid to jump without getting an 'OK' from [Rep. Alexandria Ocasio-Cortez (D-N.Y.)], I think you have a lot more open rein to attack her because she's not going to work with him anyway."