WASHINGTON (Reuters) - Republican presidential front-runner Donald Trump waded into politically risky territory this week when he accused Democrat Hillary Clinton of exploiting her gender to win votes and said she would have little support if she were not a woman.

As Trump and Clinton, fresh off big wins in five Northeastern state primaries on Tuesday, circled each other for a potential matchup in the Nov. 8 U.S. presidential election, his comments portended what could be an unusually nasty campaign.

Like other controversial remarks during his White House campaign, Trump’s comments drew criticism from a wide spectrum but also reinforced his image - which has been attractive to some supporters - for plain talk that defies political norms.

“The only thing she’s got going is the fact that she’s a woman,” Trump, 69, said on Thursday on NBC’s “Today” show, refusing to back down from targeting Clinton, 68, for what he called “playing the woman’s card.”

Trump’s remarks, reaching into an area of gender attacks that is conventionally seen as off-limits, energized Democrats.

“Keep talking, Donald Trump,” Democratic Committee National Chairwoman Debbie Wasserman Schultz told CNN on Wednesday. “Every single day when Donald Trump opens his mouth, he does more to alienate women.”

Trump, unfazed by the criticism, told supporters in Evansville, Indiana, that he has gotten a bad rap.

“Nobody cherishes and nobody respects women more than Donald Trump,” he said after being introduced by famed former Indiana University basketball coach Bobby Knight. “I will be so much better to women than Hillary Clinton.”

Trump, who can be as free with his personal attacks on men, has consistently polled poorly with women. Democrats and Republicans both accuse Trump of sexism over verbal insults lobbed at Fox News anchor Megyn Kelly and former Republican presidential candidate Carly Fiorina.

On Wednesday, Trump’s closest Republican rival, U.S. Senator Ted Cruz of Texas, named Fiorina, 61, as his running mate should he win the party’s nomination, a move that could help him draw women’s support.

“Donald has a problem with strong women,” Cruz, 45, told reporters in Fort Wayne, Indiana, before a rally. “This is not subtle, it’s not complicated.”

Republican U.S. presidential candidate Donald Trump delivers a foreign policy speech at the Mayflower Hotel in Washington, United States, April 27, 2016. REUTERS/Jim Bourg

U.S. Democratic Senator Barbara Boxer, who fended off a 2010 Senate challenge from Fiorina, said Trump is insulting all women when he attacks Clinton and other prominent women, such as Kelly, in this way.

“Either Trump has spent too much time in his Trump Tower and has no clue about what’s happening, or he truly dislikes women and are quite threatened by them,” Boxer said on MSNBC.

‘BREAKING ALL THE RULES’

But Trump said women would support his positions on security and jobs. U.S. Representative Renee Ellmers, a Republican who has endorsed him, said she believed Trump could overcome his unpopularity with women voters with his straight talk.

“To me, this is breaking all the rules, this is going against any of the typical history books and elections of the past,” she said.

Trump’s top aide and other supporters said focusing on Clinton’s gender was part of Trump’s emerging strategy for the general election and that he had no intention of hewing to traditional rules.

“When he is attacked, he will respond,” Trump’s campaign manager, Corey Lewandowski, told Reuters. “The campaign is going to proceed under the mantra, which we’ve had in this campaign from Day One, which is: Let Mr. Trump be Mr. Trump.”

A Reuters/Ipsos poll this month showed a big gender gap in opinions about Trump. About two-thirds of women had an unfavorable view of the billionaire businessman and former reality TV star, while 54 percent of men had a negative view of him.

In her political career, Clinton has sometimes benefited from missteps by male candidates. Her 2000 U.S. Senate rival, New York Republican Rick Lazio, was seen as a bully when he stepped close to her on stage during a debate to demand she sign a pledge.

Early in her first presidential campaign in 2008, Clinton accused her male opponents of “piling on” and said that would prompt more women to support her. Then-Senator Barack Obama’s comments during a debate in New Hampshire that year that she was “likable enough” were seen by some as patronizing, and as helping her win the state’s primary.

If Trump wins the nomination, his willingness to raise Clinton’s gender and other issues could make for one of the most contentious general election campaigns in recent history.

“I don’t think there’s going to be any taboos with Donald Trump,” said James Pethokoukis, a scholar with the conservative American Enterprise Institute. “He’s not going to treat her with any sort of kid gloves.”

Retired U.S. House Speaker John Boehner, a Republican, weighed in on the presidential race during a talk at Stanford University on Wednesday, according to the student newspaper, saying he could vote for his golfing and “texting buddy” Trump but harshly criticizing Cruz.

“Lucifer in the flesh,” Boehner said of Cruz, who is a staunch fiscal conservative and who angered many of his colleagues in Congress by leading a government shutdown in 2013.

“I get along with almost everyone, but I have never worked with a more miserable son of a bitch in my life,” Boehner said.

Cruz said Boehner was allowing “his inner Trump” to come out.

“What made John Boehner mad is that I led a movement of the people to hold Washington accountable,” Cruz told reporters.