The night of Donald Trump’s big Indiana Republican primary win, Sen. Elizabeth Warren, D-Mass., was ready. She tore loose with a series of late-night anti-Trump tweets in which she accused him of racism, sexism, xenophobia, narcissism and a host of other faults.

Two weeks earlier, after being asked about another Warren tweet storm in which she accused him of being "a loser," Trump fired a warning shot across Warren's bow. "Who's that, the Indian? You mean the Indian," he responded, referring to a well-known political controversy over Warren claiming Indian heritage.

The exchanges signal the start of what could be a nasty surrogate side-battle as the general election campaign begins to take shape. Warren is poised to be an aggressive Trump critic, for the Democrats and Hillary Clinton, should she lock up the nomination. And for Trump, who thrives off detecting weakness and pouncing, Warren is a target-rich environment.

From 1986 to 1995, she listed herself as a minority in the Association of American Law Schools directory. Harvard Law School cited her alleged Indian heritage in dealing with criticism that it lacked a diverse faculty. Her recipe in the "Pow Wow Chow" cookbook became the subject of derision, after charges it was plagiarized from a New York Times cookbook.

"I think she's a fraud," said longtime nemesis and Boston conservative talk radio host, Howie Carr. "I think her entire success in academia and in politics is based on a lie that she's a Native American. She refuses to take a DNA test. She doesn't even call herself Native American, anymore," he said.

Asked what the purpose of that alleged fraud would have been, Carr said, "She was basically going nowhere in her academic career. She was an instructor at the University of Texas Law School in Austin. Suddenly she began checking the box and she was a tenured professor first at the University of Pennsylvania, and then she got a job at Harvard University law school. "

Warren's office did not respond to requests for an interview. Adam Green of the Progressive Change Campaign Committee, a grassroots organization that raised over a million dollars in small donations for Warren's Senate campaign against Scott Brown, believes that Warren relishes baiting Trump and welcomes renewed scrutiny, should it come. 

"The more that Donald Trump takes the bait and attacks Elizabeth Warren, and thrusts Elizabeth Warren to the center of the national dialogue, the better for Hillary Clinton because the issues that Elizabeth Warren is fighting for are overwhelmingly popular with general election voters -- from expanding Social Security to alleviating student debt to taking on the big Wall Street banks," he said. 

Her critics, among them former Massachusetts Sen. Scott Brown, whom she beat in the 2012 Senate race, suggest Warren's Twitter tear is not accidental. "She's been getting on Twitter more and more and criticizing Trump like she is the pit bull for the Democratic Party, the Democratic National Committee, and, I would suspect, Hillary Clinton," he said.

Carr added, "I think Hillary Clinton is giving her instructions. She's going to put on her war bonnet and go out and attack Donald Trump."

One of the ironies of this fight is that the two are vying, at least in part, for the same voters – blue-collar workers and swing-state independents who may well decide the election.

Trump is trying to pull them right with promises of more coal and less regulation, while Warren, with her strong progressive bona fides, is pulling left with a call for more government safety nets and regulation.

Doug McKelway joined Fox News Channel (FNC) in November 2010 and serves as a Washington-based correspondent. Click here for more information on Doug McKelway