By Steve Holland

WASHINGTON (Reuters) - President Donald Trump may not have planned it this way, but his attacks on four liberal lawmakers as un-American have emerged as a major strategy of his 2020 re-election campaign, and more thunder from him was expected at a rally on Wednesday night.

Despite criticism from Democrats that his attacks are racist, Trump has intensified his portrayal of the four minority congresswomen as people who should leave the country if they do not like his policies on issues such as immigration and defending Israel.

The aim, one source close to Trump said, was to make Democrats look as far left as possible to moderate voters as he girds for a tough re-election battle in November 2020.

"He is trying to make them the face of the Democratic Party as we move closer into the 2020 cycle and he’s trying to highlight them as a fringe crowd as much as possible so it turns off your middle-of-the-road voters," the source said.

Trump forecast more talk about the four congresswomen at a campaign rally in Greenville, North Carolina, at 7 p.m. (2300 GMT).

"Lots of great things to tell you about, including the fact that our Economy is the best it has ever been. Best Employment & Stock Market Numbers EVER. I’ll talk also about people who love, and hate, our Country (mostly love)!" he tweeted.

Trump tweeted on the weekend that the four progressive lawmakers, known as "the squad" - Representatives Ilhan Omar of Minnesota, Alexandria Ocasio-Cortez of New York, Rashida Tlaib of Michigan and Ayanna Pressley of Ohio - should "go back" where they came from, even though all are U.S. citizens and three are U.S.-born.

The attacks initially caused some heartburn for Trump advisers who felt he had gone too far. But two advisers said Trump's subsequent tweets had since offered a contrasting view, that the four's political views were socialist, out of the mainstream and hateful to their home country, compared with that of the president and his flag-waving rhetoric.

"If the American people have to choose between the squad and the president, then that's an easy decision for voters to make," said one adviser.

WINNING TACTIC?

Trump, who during his 2016 campaign voiced harsh assessments of the state of the country, followed up his tweet on Wednesday with a video that featured patriotic scenes of Trump meeting Americans, with frequent images of the American flag. It ended with the slogan: "America - One Squad Under God."

The tactic follows a well-worn path for Trump, who called for a ban on Muslims entering the United States during his 2016 campaign. His proposal drew widespread criticism at the time, but Republicans overwhelmingly supported it, and it was a factor in his victory that year.

Over the weekend, Trump inserted himself into what had been an internecine Democratic Party fight that pitted Omar, Ocasio-Cortez, Tlaib and Pressley against House of Representatives Speaker Nancy Pelosi, who publicly questioned their influence among fellow House Democrats.

Traditionally, politicians feel they gain most when they remain silent as their opponents fight among themselves. But Trump, never one to resist stirring up a firestorm, weighed in like a charging bull.

He first defended Pelosi, then attacked the four. That prompted Pelosi to switch tactics and defend her flock, prompting Trump and other Republicans to argue the squad's attempts to push the Democratic Party to the left were working.

His attacks had a spur-of-the-moment quality to them that the Republican Party later built a strategy around.

Barry Bennett, who advised Trump's 2016 campaign, said the tactic had worked. "The Democratic Party last week was trying to distance itself from the squad, and this week they’re hugging them, and that is a massive win for Trump," he said.

But not all Republicans were comfortable with the approach.

"I'm disappointed in the tweets," said Steve Duprey, a member of the Republican National Committee from New Hampshire.

"I know the president is subject to lots of attacks, but he should always try to turn the other cheek and take the high road in my view," Duprey said.

(Reporting by Steve Holland; Editing by Kevin Drawbaugh and Peter Cooney)