Facing a tough re-election campaign in 2012, Sen. Claire McCaskillClaire Conner McCaskillGOP senator rips into Pelosi at Trump rally: 'It must suck to be that dumb' Iranian attacks expose vulnerability of campaign email accounts Ex-CIA chief worries campaigns falling short on cybersecurity MORE (D-Mo.) tried to set herself apart from President Obama on Sunday.

Appearing on "Fox News Sunday," McCaskill said that she'd voted against the president on cap-and-trade, the second round of cash-for-clunkers, comprehensive immigration reform and every omnibus bill.

McCaskill said she'd also sometimes disagreed with Obama when he was a senator.

"My record of independence, frankly, stretches back for a long period of time," she said.

When asked to name an issue where Obama had fallen short, the senator said his move into healthcare legislation at a time when he should have been focusing on job creation was "very difficult," and therefore economic issues "didn't get the attention they needed."

The National Republican Senatorial Committee is already going after McCaskill, recently for pushing the stimulus bill with Obama.

"I'm anticipating being an underdog in the this election, which means I'm going to have to work twice as hard," McCaskill said. "Which is OK with me."