Comedian Bill Maher on Monday defended his donation to Priorities USA Action, warning liberals that President Barack Obama's victory in the 2012 elections wasn't "in the bag."

Maher shocked audiences around the world last week when he announced he’d be donating $1 million to the pro-Obama super PAC.

"I promise you when it comes to election night, it's going to be neck and neck," Maher said Monday on MSNBC's Hardball with Chris Matthews.

"Obama had a giant money advantage last time because the most anybody could give was $2,300. Now Sheldon Adelson talks about giving $100 million. The game has changed from small contributions to large contributions, in the millions, the many millions. He is going to have a tremendous financial disadvantage."

The Supreme Court’s Citizens United ruling in January 2010 gave rise to super PACS, which can raise an unlimited amount of money to influence federal elections, so long as they do not directly coordinate with a candidate’s campaign.

"I always talk about the Republican bubble that they live in. But there's a bit of a liberal bubble too," Maher added. "They hear Rick Santorum talking about the father of lies and how college is bad and they think 'these people are nuts' but half the country doesn't think its nuts."

He also said Republicans were running against "a fictional president."

"A president who has slashed defense, who has raised taxes, who goes around the world apologizing, who coddles terrorists, all of which of course never happened," Maher explained. "But that's who they think the president is."

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