WRAPUP 2-Obama tries to wrest McCain's 'Straight Talk' mantle

(Updates with CNN figures on North Carolina polls)

By Caren Bohan

INDIANAPOLIS, May 3 (Reuters) - White House hopeful Barack Obama sought on Saturday to wrest away rival John McCain's key campaign theme, casting himself as the "Straight Talk" candidate willing to level with voters about tough choices facing the country.

In recent days, Democrat Obama has been hammering away at the presumptive Republican nominee over his plan to offer voters a temporary "holiday" from the gasoline tax.

McCain, an Arizona senator, says the holiday is needed give cash-strapped consumers relief from surging costs at the fuel pump during the busy driving season.

Campaigning in Indiana, Obama said the gas tax reprieve would barely help Americans' budgets and would not address the long-term problem of U.S. addiction to Middle East oil.

"It's a shell game -- literally," Obama told an audience at an Indianapolis high school. "If we want to take a permanent holiday from our oil addiction, we can finally get serious about energy independence."

As he tried to retool his message after a series of setbacks and sliding poll numbers, Obama also targeted Democratic rival Hillary Clinton's support of the tax holiday. The two face primary elections on Tuesday in North Carolina and Indiana, the next steps in their protracted struggle for the right to run against McCain in the November election.

Clinton, a New York senator, told a rally in Wake Forest, North Carolina, "These prices that are going up from ... gas prices, to grocery prices, are really taking a big chunk out of people's disposable income.