It all depends on how outraged the American People are, and how outraged the Democrats get.
Which will wholly depend on, as I've already explained, the speed of the investigation. "Outrage" these days is manufactured and manipulated for partisan political purposes more than any other time during the Republic's history than perhaps the run up to the Civil War. Expecting that there be actual outrage over a rather convoluted series of events without parties with a political agenda fueling that outrage is more than naive.
Novak is the key. He's the man Libby and Rove leaked the information to and, if he stands on his First Amendment rights as he did in the OTL, the investigation isn't moving past Novak any time soon. Nearly four years passed between Novak's initial column and the start of Libby's trial while various parties, including Plame and Wilson themselves, doing everything they could to keep the issue front and center. In the end, no one cared aside from some various political weenies and when Bush commuted Libby's sentence there was barely a whimper.
No one really cared from the beginning. In the public's perception, it was a case of a group of political scumbags playing the usual scumbag political tricks for the usual scumbag political reasons only to be caught by the other group of political scumbags who then investigated the affair and partially prosecuted it for their own scumbag political reasons. Street killings by rival crack dealers are seen in a better light than that.
If the scandal is to cause more problems, it's going to have to unfold far more rapidly before the public's understandable ennui regarding manufactured and inflated political scandals takes hold. The scandal needs to get pass Novak to get the necessary speed and that's very unlikely. As I pointed out, Novak himself is still lying about the affair.
If they used Iraq and Plamegate as an issue, they would most likely win. (IOTL, Kerry backed the war from the beginning, so Iraq wasn't an issue.) If they sweep the White House, House and Senate...
What time line are you from? The Dems cannot use Iraq because they willingly drank the kool aid, signed off on the whole disaster, and are in it up to their hypocritical little necks. Plamegate can't be an issue either as it won't to break in time for the election cycle unless Novak somehow does.
Like their fellow kleptocrats across the aisle, the Democrats are a great many things and fucking stupid isn't on that list.
After watching the GOP impale themselves on Clinton's impeachment less than a decade earlier, the Dems aren't even going to be within the same time zone as an impeach Bush movement absent collective cerebral trauma.
Plamegate won't get anyone apart from Libby or cause any real problems for the Bush Administration unless Novak rolls over. If that happenes, there are enough cutout men involved who'll sacrifice their careers to limit the damage.