Write him in! No, not for mayor, of course, because term limits make it illegal for Rudy Giuliani to be elected mayor. So let's do the next best thing in tomorrow's primary: Let's write him in for Public Advocate. Sure, you might say (as my wife just did), "Who cares about Public Advocate?" But what better way is there to show our gratitude for the magnificent job the mayor has done since the inhuman atrocities of two weeks ago? What better way is there to show the terrorists that New York is so committed to rebuilding that we will retain the most potent symbol of that rebuilding? Unfortunately, the "Keep Giuliani" movement is in disarray -- thanks to Governor Pataki. After rejecting a delay in tomorrow's primary or overturning the ridiculously confining term-limit law, Pataki announced, "If I were a resident of New York City, I'd write him in" for mayor. Oy! What was that man thinking?! By law, Mayor Giuliani can not serve a third consecutive term -- even if every registered voter in the city writes him in, even if every other candidate drops out, and even if Jesus Christ appeared in the rubble of 1 World Trade Center wearing a "Rudy for Mayor" button. Yet how many people, hearing the governor's advice, will waste their vote by writing in Rudy for mayor tomorrow? I mean no disrespect to the governor (this time, at least). Even though he's had his share (and the next guy's share) of conflict with the mayor, Pataki was merely responding to the prevailing mood of the city right now. Indeed, I have Democratic friends who wouldn't have voted for Giuliani for recording secretary of the 78th Precinct Council two weeks ago, yet been impressed by the mayor's quiet humanity and quaint humility since the attack. And, as someone who spent most of last week too depressed to even get out of bed and too scared to function without caffeine or lager, I am impressed simply by the way he is able to work through the catastrophe. "If he's less than 100 percent approval rating, it's only because someone doesn't understand the question," said Mickey Carroll, director of the Quinnipiac University Polling Institute. Hence, this MetroGnome crusade to make Giuliani our next Public Advocate. This column has had success in past crusades: Last year, I asked you to lie on your census forms so that New York could get its fair share, and, sure enough, the population of the five boroughs surpassed 8 million for the first time in the city's history. My apologies, of course, go out to Assemblyman Scott Stringer, who is the most qualified for the post, and civil liberties lawyer Norman Siegel, who would be the most fun -- but drastic times deserve drastic measures. And let's remember, this year's Democratic primary to be the city's second-ranking official is a joke. The most-recent poll showed that no candidate had the support of more than 12 percent of the voters, and only 600,000 registered Democrats expected to go to the polls tomorrow. So if everyone who reads this article (or, more likely, flips PAST this article on his way to the classifieds) writes-in Giuliani tomorrow, he'll surely win. Writing in candidates is notoriously difficult, so I called Board of Election spokeswoman Naomi Bernstein for a primer. First, she assured me that pens are provided by election workers (in other words, bring a pen with you!). To write-in a candidate, find the silver button on the left side of the voting booth (the one that will invariably be marked with a label that says "Supplemental Selection Mechanism" in Swedish). Press the button and move the slot so that it matches the corresponding office. Write in the name "Rudolph Giuliani" -- anything but an exact match, Bernstein said, could be challenged -- and pull the red lever to lock in your vote. So let's do it, New York. Let's not let Mayor Giuliani leave city government to write unreadable books or sit on useless corporate panels when we need him most. Write him in. But remember, for Public Advocate. --30--