Democrats: I can beat Republican McCain. No, I can

MYRTLE BEACH, S.C. (Reuters) - Republican presidential candidate John McCain may or may not be his party's front-runner, but Democratic rivals treated him like the man to beat at a debate on Monday.

McCain, an Arizona senator who is leading national polls based on victories over his Republican rivals in New Hampshire and South Carolina, came up often at the Democrats' debate.

Former North Carolina Sen. John Edwards, who is running a distant third behind Democratic rivals Hillary Clinton and Barack Obama, argued that while Clinton and Obama may attract support in big cities, he could gain support in rural areas where McCain would be appealing.

"I grew up in the rural South, in small towns all across the rural South, and I think I can go everywhere and compete head-to-head with McCain," Edwards said.

Hang on a second, said Clinton, a New York senator who would be the first woman U.S. president.

She said if McCain were to be the Republicans' choice, the general election would probably be mostly about national security, and she thought she would be better positioned to run against him if that were the case.

"I believe of any one of us, I am better positioned and better able to take on John McCain or any Republican when it comes to issues about protecting and defending our country," she said.

But Obama, who would be the first black U.S. president, said he would be in better shape to campaign against McCain because he had opposed the Iraq war from the start. Clinton had voted for the 2003 Senate resolution that authorized the use of U.S. force against Iraq.

McCain has been a strong proponent of the U.S. troop build-up that has brought a measure of stability in Iraq, while a fierce critic of former Defense Secretary Donald Rumsfeld's conduct of the war before the build-up was ordered.

"I believe that the way we are going to take on somebody like a John McCain on national security is not that we've been sort of like John McCain," said Obama, a U.S. senator from Illinois. "I think it's going to be somebody who can serve a strong contrast."

Neither party has established a clear front-runner in the race to pick the two candidates to contest the Nov. 4 presidential election. (Writing by Steve Holland)