As he looks towards the almost certain presidential battle this fall between billionaire businessman Donald Trump and former Secretary of State Hillary Clinton, political analyst William Galston says he’s reminded of an old political maxim: “Never wrestle with a pig because you’ll just get muddied -- and the pig will love it.”

Galston, a former policy adviser to President Bill Clinton, and other political experts agreed on Wednesday that the nation is likely to be treated to one of the dirtiest presidential campaigns on record. “I think this will be an historically dirty campaign, and we’ve had some bad ones,” said veteran pollster John Zogby. “This will be historically and classically bad, because Trump has no filter whatsoever. He is constantly on the offense even when he’s on the defense.”

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The blustery, outrageously insulting Trump destroyed GOP opponents throughout the 2016 campaign season with relentless attacks: Think “low energy” Jeb Bush or “lying Ted Cruz” or “little” Marco Rubio or physically unappealing Carly Fiorina with “that face.”

The general election campaign this fall may be like nothing Americans have seen since the 1964 clash between Democratic President Lyndon B. Johnson and conservative Republican challenger Barry Goldwater. That’s when the Democrats aired a controversial TV ad implying that Goldwater would unleash nuclear war if he were president. You would have to go back to 1884 to find an even dirtier campaign. Voters were treated to a slugfest between Democratic nominee Grover Cleveland and Republican James Blaine – one that was rife with charges of graft and corruption and Cleveland’s illegitimate child.

Even before he came close to locking up the GOP nomination Tuesday night with victories in Florida, North Carolina and Illinois, Trump began blasting Clinton as likely jailbait because of her mishandling of sensitive government email during her tenure at the State Department. He also denounced her as a hypocrite for calling him a sexist in light of her husband’s White House sex scandal involving a young intern, Monica Lewinsky. Trump also startled many last December by declaring it was “disgusting” that Hillary Clinton took a bathroom break during a Democratic presidential debate.

“He can brook no criticism, and all he knows how to do is counterpunch,” Zogby explained Wednesday. “And it’s no-holds barred. So this will be Monica’s blue dress, this will be [Bill Clinton’s] bimbo eruptions, this will be the Clintons’ White Water [business deals in Arkansas] and we haven’t even gotten to Benghazi yet.”

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Trump insists he’s spoiling for a direct fight with Clinton who currently far exceeds Sen. Bernie Sanders of Vermont in the delegate count for the Democratic nomination. “I haven’t even focused on Hillary Clinton,” Trump has said repeatedly, including during an appearance on ABC’s Good Morning America March 1. “I can tell you the one person that Hillary Clinton doesn’t want to run against is me.”

Clinton, of course, is no shrinking violet and she has plenty of material about Trump to work with—if she chooses. That could range from the extramarital affairs of the thrice-married Trump to allegations of high-pressure sales tactics at the now moribund Trump University to the seemingly endless stream of insults against Hispanics, Muslims, women and even disabled people. She boasted recently of having a “thick skin” after 25 years of weathering conservative attacks against her and her husband, and she said that she was eager to begin drawing sharp contrasts between herself and Trump on policy, government experience and temperament.

“When we hear a candidate for president call for the rounding up of 12 million immigrants, banning all Muslims from entering the United States…when he embraces torture, that doesn’t make him strong--it makes him wrong,” Clinton said Tuesday night during her victory speech in West Palm Beach, Florida.

What’s more, most recent polls suggest that Clinton would beat Trump in a head-to-head matchup this fall, if they become their parties’ nominees. A recent CNN/ORC poll, for instance, shows Clinton easily topping Trump in a matchup, 52 percent to 44 percent, while Sanders, the Vermont democratic socialist senator, would beat Trump as well, 55 percent to 43 percent.

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“I think she is every bit as tough as Trump is,” said former House member Martin O. Frost of Texas, a lawyer and one-time Democratic leader who has been involved in presidential campaigns dating back to the late 1960s. “And anybody who doesn’t understand that hasn’t been paying attention. It’s just a question of how mean and ugly he makes this race.”

“You are talking about two universally known figures here,” David Axelrod, a Democratic strategist and former Obama campaign advisers, told The New York Times yesterday. “The strong feeling that each generates is unusual.”

Clinton has dismissed Trump as a bully and public policy ignoramus who is more comfortable riling his supporters and targeting protesters with threats of violence than engaging in thoughtful debate over the economy, immigration, health care and national security.

Tough talk by Clinton is one thing, but going head to head with the blustery billionaire is something quite different.

As he demonstrated in demolishing the short-lived campaign of Fiorina, the former Hewlett-Packard CEO, Trump has no compunction about belittling or attacking a woman on the campaign trail or in a nationally televised debate. Whether that tactic would work against Clinton remains to be seen. She won her first term as senator in 2000 after her GOP rival, Rick Lazio, became too aggressive during a televised debate. Getting down in the gutter with Trump would be a major mistake for her, some experts warn, and Clinton would be well advised to leave most of the dirty work to her surrogates or vice presidential nominee.

Zogby recalled what happened to Rubio, the Florida senator who recently gambled by exchanging barbed, personal insults with Trump in a nationally televised GOP debate from Detroit and during subsequent campaign appearances. Trump gained the upper hand in those exchanges before driving Rubio out of the race with a solid victory in Florida Tuesday.

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What’s more, Trump is practiced in delivering withering assessments of Clinton’s career as First Lady, a New York senator and finally Secretary of State. He insists that she failed miserably in pressing for national health care reforms during her husband’s administration, and that she erred as a senator in supporting the U.S. invasion of Iraq. Just as Sanders is doing, Trump has criticized Clinton for having supported NAFTA and other international trade deals that cost millions of US jobs. And Trump contends that Clinton was wrong to help convince President Obama to support military action in Libya.

All of these moves were “disasters,” Trump insists, and Clinton will go down in history as the “worst” Secretary of State.

But Frost argues that Trump would enter the race with huge negatives, especially among minority groups and illegal immigrants he has targeted as criminals and rapists. While he has generated enormous Republican enthusiasm for his pledge to “Make America Great Again,” knock the “crap” out of terrorists, and negotiate “great” trade deals with our allies, polls suggest that Trump is even more unpopular with the American public overall than Clinton, who many distrust or dislike.

What’s more, Trump would probably get limited mileage out of attacking her on her email woes – especially if the FBI concludes in the coming months that she did nothing illegal -- or mocking the record of Bill Clinton. Trump has done best when he divides his enemies and taps into the anger of many of the “forgotten” Republicans, conservative Democrats and independents, who are fed up with the status quo and are energized by Trump’s political “outsider” message.

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“There are some interesting issues here, some of which don’t work as well for Trump in the general election as they did in the primary,” Frost said. “But the anger issue – stoking the resentment of blue collar, non-educated whites who say they are somehow being screwed by the system – if that’s the kind of campaign he runs; it will be mean and ugly.”

And as Galston, a Brookings Institution political policy expert, noted, “I think his key electability weakness is the very long list of voters he’s insulted and attempted to marginalize.”