Peter A. Brown, assistant director of the Quinnipiac University Polling Institute and former editorial writer for the Orlando Sentinel, notes that when it comes to Rudy Giuliani’s presidential prospects, the barometer of conventional wisdom has shifted radically in his favor.

The expert’s take, as printed in the Post Bulletin, is that the ex-mayor’s current surge in the White House futures market is worth taking seriously, but with a large grain of salt.

That’s because it is unclear whether Giuliani’s rise in the polls is based on most voters having enough information about him to make the same decision they will when they actually cast ballots early next year.

Saturday, Reuters reported Giuliani, who found himself virtually tied with John McCain in a January poll, now holds a shocking 25-point lead over the Arizona senator in a recent survey.

Among registered Republicans, 59 percent said they backed the former New York City mayor and 34 percent favored McCain, who announced Wednesday he would seek the presidency, the Newsweek poll found.

According to Brown, there are two key unknowns about Giuliani’s numbers:

• Is he leading because most Republican voters don’t know about his messy personal history and positions on social issues - or are they aware and believe his positive attributes outweigh these perceived drawbacks?
• Will his wide margin over potential Democratic opponents in the general election, based on the perception that he is a strong, experienced leader, withstand the scrutiny of a presidential campaign?

We won’t know for some time, probably until voters begin having their say in the primaries and caucuses. All candidates have unknowns. What makes Giuliani’s situation murkier is that his popularity stems from rhetorically standing up to terrorists after 9/11.

Otherwise, there is little public knowledge of his views and background - at least outside the New York metropolitan area.

These questions are probably too difficult to get at until Giuliani has endured a news media barrage and negative attacks from his opponents.

No independent pollsters are likely to simulate negative information given voters during a campaign before asking which candidate they support. That would subject the pollsters to charges of loaded questions.

Of course, pollsters working with various candidates will definitely go that route, as they don’t disclose their results publicly, and need to know how to advise the clients who pay them big bucks.

Regardless, Giuliani is the hot candidate in the 2008 presidential election - so much so that conservatives who gave him no chance for the GOP nod just a few months ago are reassessing their views.

In virtually all polls, he is beating John McCain, who conventional wisdom installed as the favorite for the 2008 Republican nomination the day after the 2004 election was over. Those surveys also generally show Giuliani with a slight lead over the Democratic aspirants.

Giuliani’s strength is his ability to appeal across party lines, running very well among independents and garnering support among Democrats.

At one point that was McCain’s strength, and he remains relatively popular among non-Republicans. But as he has accentuated his support for the Iraq war, opposition to abortion rights and efforts to mend fences with right-wing leaders, his appeal to Democrats and independents has waned.

The conventional wisdom had been, until recently, that Giuliani’s support for abortion rights, gay rights and gun control would make him somewhat of a pariah among Republican primary voters who, for the most part, take opposing views.

But there is substantial animosity among many conservatives toward McCain, who over the years has relished his maverick image and his willingness to challenge GOP orthodoxy.

Amazingly, a recent national Gallup Poll conducted among Republicans found that they overwhelmingly consider Giuliani more likeable, better able to handle a crisis, a stronger leader and a better manager than McCain.

Among Republican voters in Ohio and Florida, the two most important swing states in the country, GOP voters found Giuliani substantially ahead of McCain. Rudy Giuliani led even among social conservatives, despite moderate views (for a Republican), admitted adultery and multiple marriages.

Although the Democratic struggle between Hillary Rodham Clinton and Barack Obama has garnered most of the media attention, the shock of the campaign thus far has been Rudy’s rise.

But any judgment on whether his chances are as strong as they appear must wait until he weathers the storm that comes with being a frontrunner.