WASHINGTON — The 2012 presidential campaign was expected Thursday to pass the $2 billion mark in fundraising, according to accounting statements submitted to the government, thanks to an outpouring of cash from both ordinary citizens and the wealthiest Americans hoping to influence the selection of the country’s next leader.

The eye-popping figure puts this election on track to be the costliest in history, fueled by a campaign finance system vastly altered by the proliferation of “super” political committees that are bankrolling a barrage of TV ads in battleground states.

President Barack Obama and Republican challenger Mitt Romney had brought in more than $1.5 billion through the end of September, according to previous fundraising reports submitted before the final pre-election accounting statements were due Thursday night. Obama hadn’t yet disclosed his fundraising for early October, but Romney’s campaign said it raised $111.8 million in the first two weeks. Added to that: more than $230 million in donations involving super PACs since 2011.

Restore Our Future, founded by former Romney aides, reported raising $110 million so far. Priorities USA, a pro-Obama group founded by two former aides to the president, reported raising $50 million through last month.

The $2 billion fundraising figure doesn’t include nearly $130 million spent on political ads by non-profit groups that aren’t required to file campaign finance reports or disclose their donors.