Somewhere, there should be a Hall of Fame honoring profoundly stupid Democratic Party campaign ideas. Among the featured exhibits would be Michael Dukakis’s 1988 tank ride and John Kerry’s 2004 Ohio duck-hunting trip. (“Can I get me a hunting license here?”)

The important thing to remember about such classic campaign blunders, however, is that Democrats didn’t realize their disastrous potential until it was too late to prevent them.

Whether it’s George McGovern’s choice of Thomas Eagleton as his 1972 running mate or Fritz Mondale’s promise to raise taxes in 1984, for some reason there’s never anybody around Democrat HQ with the foresight to shout an advance warning.

If Sen. Barack Obama’s presidential campaign melts down this year, however, the Democrats won’t have that excuse. This time, there was plenty of warning:

* Writing at the Huffington Post, Hillary Clinton supporter Larry Johnson declared on Feb. 16 that Obama’s association with former Weather Underground terrorist Bill Ayers “will be Barack Obama’s Willie Horton.”

* On March 13, ABC News was the first major media outlet to report on the anti-American rants of Rev. Jeremiah Wright, the pastor of Obama’s Trinty Church in Chicago, igniting a controversy that continued to make headlines for weeks.

* On April 7, Christopher Hitchens noted that Obama had named a radical Catholic priest, the Rev. Michael Pfleger, among his religious “mentors,” and that Pfleger had defended Nation of Islam leader Louis Farrakhan. On May 25, Pfleger preached a bizarre sermon at Trinity church, mocking Hillary as an advocate of “white entitlement,” resulting in a YouTube video clip that quickly went viral — like the plague — on the Internet.

* Obama’s connection to corrupt Chicago Democratic fund-raiser Tony Rezko was widely reported by major media. In January, for example, ABC News reported that Rezko and his associates had “contributed more than $120,000 to Obama’s 2004 campaign for the U.S. Senate, much of it at a time when Rezko was the target of an FBI investigation.”

His scandalous associations didn’t stop Obama from squeaking past Hillary to clinch the Democratic nomination, but his responses to these controversies so far — such as first “distancing” himself from Wright, then finally quitting the Trinity congregation — are unlikely to immunize him from further scrutiny in the general-election campaign.

ONLY ONCE DURING a Democratic debate, in Philadelphia on April 16, was Obama asked to respond to questions about these controversies. His staunchest supporters admitted that Obama fared very poorly in that debate, and he then refused subsequent debate invitations — an option he won’t have this fall.

Even the manner in which Obama won the nomination suggests that he may prove an unusually weak candidate in the general election.

Because of the front-loaded primary schedule, more than half of the Democratic delegates were chosen by the time the “Super Duper Tuesday” primaries were concluded on Feb. 5. Moreover, Obama’s advantage in pledged delegates was won in caucus states — where organization among party activists is the key — rather than in primaries, which test a candidate’s appeal to ordinary voters.

As the primary schedule continued beyond Super Tuesday, Hillary won every major “swing state” (including Ohio, Pennsylvania, West Virginia, and Kentucky) and exit polls consistently showed her the stronger candidate among the blue-collar constituency that is crucial to any Democratic victory.

When the primary campaign ended, Obama’s lead among the more than 3,400 pledged delegates was a scant 120, and he was 300 delegates short of a nominating majority. Thus, with the help of the May 31 ruling that limited the Michigan and Florida delegations to 50 percent representation at the convention, the Democratic “superdelegates” ultimately picked the nominee, infuriating Hillary’s female supporters.

ALL OF OBAMA’S problems would be enough to worry Democrats if he were a veteran politician, but he’s not. He’s a 46-year-old former state legislator who was only elected to the Senate in 2004 and whose presidential candidacy got an artificial boost from media enthusiasts like Oprah Winfrey and Chris Matthews.

Obama’s nomination is part of a pattern of Democrats preferring “fresh new faces” as their presidential candidates. McGovern, Jimmy Carter, Dukakis and Bill Clinton all won the nomination on their first attempts.

By contrast, Republicans have tended toward the “it’s his turn” approach to their White House candidates. Excluding only vice president Richard Nixon’s 1960 campaign and the historical anomaly of Gerald Ford, George W. Bush was the first GOP presidential candidate since Dwight Eisenhower to get the Republican nomination on his first try.

Strong opposition from conservatives was not enough to stop Sen. John McCain from becoming the GOP’s latest “it’s his turn” candidate — worrying many Republicans who see similarities to Sen. Bob Dole’s weak 1996 campaign.

In addition to his shaky standing with conservatives (Tom DeLay’s wife recently declared she’ll vote for Libertarian candidate Bob Barr), McCain has other obvious weaknesses. He’s 71 years old, short and bald, and seems a poor match for Obama’s charismatic personal presence.

However, the “it’s his turn” approach means that McCain is already a familiar character to independent swing voters, who typically pay less attention to politics than do avid partisans of either party. Such scandals as his membership in the “Keating Five” are all old news, and it’s unlikely the fall campaign will produce any shocking revelations about the Republican. Democrats can’t say the same about the untested Obama.

Beyond McCain’s shortcomings as a candidate, however, Democrats are encouraged by numerous harbingers of an anti-Republican trend in November. The GOP trails in fundraising, the economy is stagnant, gas is now over $4 a gallon, more than 100,000 U.S. troops are still in Iraq, and the potentially poisonous “wrong direction” poll numbers are disastrously high.

YET THESE ILL omens for Republicans may have inspired in Democrats an overconfidence that made Obama’s weaknesses too easy to overlook — again, repeating the pattern of their previous disasters.

In August 1972, Hunter S. Thompson recalled a conversation with McGovern campaign manager Gary Hart: “One of his central beliefs for the past two years had been that winning the Democratic nomination would be much harder than beating Nixon…. So any Democratic candidate could beat Nixon, and all the candidates knew it.”

The Democrats’ confidence in Obama may yet be vindicated. If not, on Nov. 5, they’ll have a new exhibit when they finally decide to break ground on their campaign blunder Hall of Fame.