Over the past few weeks, I’ve wrestled with the feeling that history will repeat itself and the Democrats once again will blow their chance to take back the White House in November.

I’ve had visions of past debacles, when the Democrats seemed to do almost everything in their power to lose the presidential election.

The years 1968 and 1988 come to mind; the thought of adding 2008 to the loser list is almost unimaginable. Yet, it seems increasingly likely. I started to wonder: Is there some self-destruct cycle that sets in motion for the Democrats every 20 years?

This presidential election, which should have been a waltz right into the Oval Office for the Democrats, now is a protracted verbal slugfest between Hillary Clinton and Barack Obama that gets uglier each day. With an endless war and a faltering economy, Democrats have plenty of ammunition to slay the GOP. But the candidates have turned on each other.

Of course it is the right of Clinton and Obama to campaign their hardest, and most Democrats could support either one of them as the party standard bearer. But the price of this longer-than-anticipated campaign could well mean a brokered convention where the “superdelegates” – officials, party leaders and others – ultimately choose the nominee. This is the scenario Clinton seems to be counting on to benefit her, despite what it costs the party and the country. She ignores clear signals from Democratic Party leaders that they want a seamless, pre-ordained coronation, not floor fights and credentials challenges.

THE STAKES ARE TOO HIGH TO GAMBLE ON A DIVIDED CONVENTION.

For his part, Obama continues amassing supporters and superdelegate commitments (though they are allowed to change their minds), and a recent Gallup poll had him 10 points ahead of Clinton, his biggest lead yet. He says it is fine by him for Clinton to continue – easy to say since he is ahead. What he should do is call on Clinton to bow out now, with grace.

The Democrats should take a lesson from the past. They must remember how often they have grabbed defeat from the jaws of victory. The stakes are too high this time to gamble on a divided, conflicted, messy convention for the entire world to see – not to mention the fact that all the sparring between Clinton and Obama over delegate counts, personal behavior and questionable friendships gives presumptive Republican nominee John McCain a huge advantage. McCain must be rubbing his hands in glee, noting what issues he can use against whichever Democrat survives.

This year, Clinton and Obama must realize their divisiveness is hurting the party. Clinton won’t acknowledge her increasingly slim chances of winning the nomination. She trails in the delegate count and should do the math. The solution to the equation does not end up in her plus column, even if she wins the Pennsylvania primary April 22. Some supporters say the best thing she could do is end her campaign, which would allow plenty of time for the Democrats to stage an all-out attack on the GOP.

But Clinton will have none of it. She told The Washington Post last week she won’t end her campaign “until we finish what we started and until we see what happens in the next 10 contests and until we resolve Florida and Michigan. And if we don’t resolve it, we’ll resolve it at the convention – that’s what credentials committees are for.”

She would do well to recall the 1988 race between Democrat Michael Dukakis and Republican George H.W. Bush. Democrats had a lot going for them, including double-digit home mortgage rates and the Iran-Contra scandal.

Dukakis was ahead by 17 points that summer; by Labor Day, the lead had vaporized. His campaign was disastrous, perhaps most memorable for him sitting in the turret of a tank, wearing combat gear, at a factory in Michigan. He looked ridiculous. Bush beat Dukakis, 53.4 percent to 45.6.

She should flash back to the 1968 Democratic convention in Chicago where anti-Vietnam War protesters were clubbed, beaten and arrested, with much of the violence televised to a horrified nation. Inside the convention hall, Vietnam also was a divisive issue. Images of violence outside and a party in disarray inside were seared on the collective consciousness.

That November, Republican Richard Nixon beat Democrat Hubert Humphrey, 43.4 percent to 42.7 percent. It’s hard not to imagine another outcome had the Democrats handled the protests better and reined in Daley.

Different scenarios from this year, to be sure, but losing scenarios nonetheless.

“We don’t want this [campaign] to degenerate to a big fight at the convention,” Democratic National Committee Chairman Howard Dean said last month.

In a National Public Radio interview April 1, House Speaker Nancy Pelosi said “it would be harmful to the Democratic Party and our prospects in November if the perception is that the superdelegates overturned the votes of the people…”

Clinton and Obama must listen to their leaders – or the 20-year losing cycle will continue its run.