Obama's healthcare law requires insurers to cover people with pre-existing conditions even if they've had a gap in their coverage or are entering the market for the first time.
The rule took effect for children aged under 19 upon implementation of the law in 2010. Denial of insurance due to a pre-existing condition will be banned for all started in 2014.
The Affordable Care Act also mandates that most Americans carry health insurance or pay a fine, and provides some with subsidies to make coverage more affordable.
Conservatives are vehemently opposed to the Affordable Care Act, arguing it will raise taxes, limit job growth and add to the deficit. The GOP-led House has voted more than 30 times to repeal, defund or dismantle it, and Republican presidential nominee Mitt Romney has said he would repeal the law if elected.
Supporters of the law say it addresses the plight of the uninsured while lowering healthcare costs and government spending.
By signing McCready's petition, users pledge "not to vote for any candidates who oppose ObamaCare."