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The country doesn't know much about Elena Kagan's legal philosophy but President Obama said this week one case offers much more than a glimpse.

"In the Citizens United case, she defended bipartisan campaign finance reform against special interests seeking to spend unlimited money to influence our elections," Obama said Monday in announcing Kagan as his Supreme Court nominee.

"I think it says a great deal about her commitment to protect our fundamental rights," he said.

The case involved a controversial movie on then presidential front-runner Hillary Clinton. A lawsuit tried to stop its distribution since the group behind it, Citizens United, was a non-profit corporation. The Supreme Court upheld Citizens United's right to distribute the movie, giving corporations and trade unions broader First Amendment rights in political advertising.

"Corporations, and trade unions going up on televisions spending unlimited amounts of money to do so and actually advocating for or against the election of a specific candidates," said Dave Levinthal, spokesman for the Center for Responsive Politics.

Kagan, who worked in the Clinton White House, argued the case against Citizens United. She clashed with Chief Justice John Roberts on whether giving the Federal Election Commission the power to silence Citizens United could trigger other forms of censorship.

"We don't put our First Amendment rights in the hands of FEC bureaucrats and if you say that you are not going to apply it to a book, what about a pamphlet?" Roberts said in the oral arguments.

"I think a pamphlet would be different," Kagan said. "A pamphlet is pretty classic electioneering."

But the president of Citizens United said Kagan's legal argument, which the president now says reflects her judicial philosophy, is cause for concern.

"It's a fundamentally flawed view of the First Amendment and I think it disqualifies her from the high court," said David Bossie, the founder and president of Citizens United.

In affirming the court majority, Roberts branded Kagan's arguments contradictory and said they invited new constitutional mistakes. Legal experts now wonder if a Roberts-Kagan clash is inevitable.

White House counsel Robert Bauer tried to minimize such fears.

"I can point to other cases where people can find a barbed quality to the way the chief justice replies," Bauer told reporters Monday. "I don't find in our conversations with others…that there is personal hostility at all."