Democrat Barack Obama's intent to remove most US troops within 16 months of taking office could be upended if Iraqi elections once again inflame ethnic tensions – especially if Al Qaeda-affiliated extremists are able to exploit them and regain a foothold.
And John McCain's assertion that he would bring US troops home "in victory" would be more difficult to justify if Iraq takes a turn for the worse.
US concerns about Iraq's political stability stem in large part, as they have in the past, from unresolved tensions along ethnosectarian divides – between the majority Shiites and the minority Sunnis, but also now between the Kurds and the Shiites.
Last week, both Gen. David Petraeus – the US commander in Iraq during the "surge" of US troops who is about to assume the top spot in the US Central Command – and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said that they see recent progress in Iraq as "fragile" and "reversible."
And Gen. Ray Odierno, the US commander in Iraq who replaced General Petraeus, is speaking publicly of his concern that power struggles exacerbated by the upcoming elections could undo recent political gains.