In May of 1988, Gov. Michael Dukakis had a 10-point lead over his Republican rival, the same margin that Hillary Clinton has today.

He lost. And she could, too.

Don't comfort yourself too much by looking at the horse race polls. Those are about Donald Trump's weakness, not Clinton's strength. A fresh Washington Post poll shows that only 37 percent of American voters trust her, and the number is dropping ---- even before her well-fed opponents have begun to pound the airwaves with slimy attack ads on her.

And let's face it: It is not beyond the imagination to think that a fresh scandal could emerge. Clinton has long been a warrior for good causes, from child poverty to health care.

But she has a slippery side, one we first saw way back in 1978 when she earned $100,000 trading cattle futures in a single year on an investment of $1,000. She made that bet on the advice of a friend who later did loads of business with the government of Arkansas during the period when the Clintons ruled. Between that stunt and the questions that now swirl around the Clinton Foundation, it's been a long and bumpy ride for her on ethics.

If John Kerry could be mortally wounded by the Swift Boat ads despite his solid record of heroism under fire in Vietnam, then Clinton can be wounded with an ad campaign about her ethics. She even helps her enemies on occasion with blockheaded moves of her own, like the decision to establish a private e-mail account or to accept $675,000 for giving three speeches at Goldman Sachs.

Clinton is also vulnerable on trade, especially in the swing states of the Midwest. Trump is engaged in classic demagoguery over this, making trade the bogeyman for stagnant incomes and sluggish mobility, as if rescinding NAFTA will lead to a golden age in America. It is mostly nonsense, but the point here is that it could work politically.

So don't rest. Yes, Clinton is the likely winner, and Trump is a buffoon. But let's not get cocky.

For Republicans, this is a gut-check moment. Trump's big win in Indiana means he will carry their banner in the fall.

If GOP voters embrace Trump, they embrace his bigotry and misogyny, his crude personal behavior, and his willful ignorance on a range of domestic and foreign policies. Is their loyalty to the party that blind? Is their hatred of Clinton that irrational?

For many Republicans, the answer will be yes. One wonders how far they would go: Would they support David Duke if he got the nomination?

But many Republicans are peeling off. An NBC News/Wall Street Journal poll in March found that 47 percent of women GOP primary voters said they could not imagine voting for Trump, along with 40 percent of men.

A growing number of Republican leaders, like former Gov. Christie Whitman, have repudiated Trump. And so far, no members of Congress have followed the lead of Gov. Chris Christie by endorsing Trump, and only three state legislators have - Sen. Kevin O'Toole (R-Essex), Sen. Mike Doherty (R-Warren) and Sen. Joe Pennacchio (R-Morris).

For Democrats and independents, the task is to unite behind Clinton. That will be a tough swallow for supporters of Bernie Sanders, especially after his win in Indiana last night. If they are tempted to sit out the general election, they need to think long and hard about Trump sitting in the Oval Office. And if Sanders pulls off a miracle, Clinton supporters need to do the same.

This moment is almost hard to believe, that a charlatan like Trump is one win away from the presidency. That puts the nation in real peril, at risk of imposing a self-inflicted wound that could tear the country apart and endanger its security.

It's time to rally. Clinton is the likely winner. But the Trump nightmare is now way too close for comfort.

More: Tom Moran columns

Tom Moran may be reached at tmoran@starledger.com or call (973) 836-4909. Follow him on Twitter @tomamoran. Find NJ.com Opinion on Facebook.