With gubernatorial challenger Dan Hynes releasing his second negative ad against Gov. Pat Quinn yesterday, the contours of the looming debate between these two candidates is becoming clear.  Watch his latest spot:

As he has done in both his ads, Hynes is going to try to out-populist the populist Quinn by slamming the tax plans the governor supported last spring as putting too much of a burden on the "middle class."  He will constantly contrast those proposals with his new plan, which would only raise taxes on those making more than $200,000 (but requires amending the state constitution).  

Meanwhile, Quinn is going to emphasize that his initial budget -- which never attracted much support among lawmakers -- would have shielded many middle-class and low-income Illinoisans from the effects of his proposed tax increase, even cutting some of their bills.  It was the General Assembly's intransigence, he will argue, that led him to eventually support other plans that provided less tax relief.

But this debate isn't really about who has the best, most humane plan to raise revenue and balance the state budget deficit.  Objectively speaking, both proposals have their merits.  The real question is: Which of these candidates can actually convince the legislature to go along?

In Quinn's case, we repeatedly criticized his handling of the negotiations last spring.  His "shared sacrifice" budget proposal, while noble in intent, had the unintended affect of alienating interests on all sides of the political spectrum and left him with no allies in the scrum.  If instead he had started the process by proposing some variation of Sen. James Meeks' plan (which he ultimately voiced support for in late May), things might have gone much smoother.

Now, supporters of Meeks' proposal have formed the massive Responsible Budget Coalition (RBC) which is preparing to push a revised version of the long-standing plan in the new year.  While Quinn hasn't fully signed on, he has indicated that he will work with the group on "refining" the legislation.  This is undoubtedly movement in the right direction.

As for Hynes, he is in the unique position of campaigning on a plan that requires implementation before he even takes office as governor.  Indeed, his proposal to move Illinois from a constitutionally-mandated flat income tax rate to a graduated system depends on securing three-fifths majorities in both legislative chambers before May of next year.  Then the voters would have to sign off on the plan at the ballot box in November.

The gubernatorial primary, however, falls on February 2.  So Hynes is essentially asking Democratic voters to choose him over Quinn on the assumption that he can garner legislative support for his plan.  At the same time, we're yet to hear of a single lawmaker in Springfield who has pledged to throw their weight behind Hynes' proposal. If he really wants to set himself apart from Quinn, he must show that he can form a large coalition around his policy prescriptions (remember, he needs a three-fifths majority in both chambers).  It's still early; but so far, he's given us no indication he can.

And what if Hynes wins the primary, but then fails to garner enough support for his legislation?  Then he has to wait until 2012 to take another shot at a constitutional amendment.  It seems fair to ask him: "If you win the primary but fail to pass your proposed legislation, what's your Plan B?"

Moreover, by incessantly slamming Quinn's purported "50 percent tax hike" in the months leading up to the primary, Hynes could actually impede the work of the RBC as they push their plan to immediately right the fiscal ship in Illinois.  That's no way to develop allies in the progressive community.

While this debate appears on the surface to be about who has the better, fairer proposal, it's really be about who has the ability to move their plan through the Springfield morass.  On this point, Hynes has more to prove than Quinn.

Full Disclosure: The SEIU Illinois State Council, which sponsors this website, has endorsed Pat Quinn in the Democratic primary for governor.