recently negotiated payroll tax cut extension, slated to expire this month.  Fair's current prediction is predicated on the assumption that Congress will not allow the cut to expire, but instead extend it to the end of 2012.  Not extending the payroll tax cut, however, says the PVE, will cost Obama 1.3 points of vote share.  And this caveat alone demonstrates the PVE's potential practical value for political strategizing.  If congressional Republicans allow Democrats' and the MSM (forgive me if I repeat myself)'s demagoguery to pressure them into extending the payroll tax cut, they could actually be helping Obama and hurting his GOP opponent. But getting back to the PVE's prediction, delve into the numbers in Fair's paper, and the magic number appears to be 3.  If the economy is growing at over 3 percent on Election Day, Obama wins; if it's growing at minus 3 percent, he loses.  And at exactly 3 percent, it's anyone's guess -- too close to call. And herein, if we take the PVE seriously, lies both a dilemma and a warning for congressional Republicans.  The dilemma is that, of course, the country must always come before politics.  Therefore, if President Obama and the Democrats propose policies and legislation that will substantively, over the long term, boost economic growth and create jobs, we Republicans obviously will have no choice but to support those policies, even if it guarantees a second Obama term. Not that this writer seriously expects that to happen, and thus the following warning: