Congress and the GOP generally are afraid of the birther issue becoming a ‘Lewinsky’, whereby they are punished for overreach and the president is forgiven in re-election.
I’d think the question is whether the bad economy and deep disagreement with his policies, such as Obamacare, could be combined with this issue—ripe, evidently substantive, but not dealt with—whereby the electorate would choose to simply vote him out of office, rather than go for the deep national division (rioting?) and potential national weakening that a Constitutional response to his apparent fraud would create.
Yeah! That will help strengthen the Constitution and rule of law. /s