Republicans won the 2002 and 2004 elections on the national security issue. Last month, White House senior adviser Karl Rove signaled that his party intends to use the same strategy this year.

"At the core, we are dealing with two parties that have fundamentally different views of the world and fundamentally different views on national security," Rove told the Republican National Committee. "Republicans have a post-9/11 view of the world, and Democrats have a pre-9/11 view of the world."

Last week, a hitherto low-key Democratic senator responded to Rove's challenge. "I say to Mr. Rove and his fellow partisan strategists, you have thrown down the gauntlet, and we intend to pick it up," Sen. Evan Bayh, D-Ind., declared in a speech in Washington.

It was the first of a series of events in which Bayh intends to do something Democrats have rarely done: Challenge President Bush head-on over his leadership in the war on terror—not just on Iraq, or warrantless wiretapping, or torture, or intelligence failures, but on Bush's defining issue, his ability to keep the country safe.

That's the only issue Bush has left. In six national polls taken last month before the State of the Union address, the president's approval rating for his handling of the economy averaged only 40 percent. On Iraq, his approval averaged 39 percent. Health care? 32 percent. In every poll, Bush scored his highest marks—averaging 50 percent—for his handling of terrorism.

Last month's ABC News/Washington Post poll asked, "Compared to before September 11, 2001, do you think the country today is safer from terrorism?" By more than 2-to-1 (64 percent to 30 percent), Americans said yes.

Rove sounds confident that security will continue to trump all other issues. Democrats should have learned by now that they cannot concede the security issue to Bush and try to win solely on domestic issues, or corruption, or even discontent with the war in Iraq. As Bayh warned, "The American people will not trust us on any of those issues if they don't first trust us with their lives."

Who is Evan Bayh to say such things?

He bears a famous political name. His father, Birch Bayh, was also a senator from Indiana; in 1976, the elder Bayh was a presidential candidate. Evan Bayh is on the Senate Armed Services and Intelligence committees. He might run for president in 2008, but he's been overshadowed by better-known prospective contenders.

But how many elected Democrats have had the guts to make the charge that the Bush administration "has undermined our nation's security and bungled the war on terror"? Sure, Bush is tough, Bayh said, calling on Democrats to reclaim the tradition of Franklin D. Roosevelt, Harry Truman, and John F. Kennedy—Democrats who led global confrontations with fascism and communism. "Tough is good," Bayh said, "but six years into the Bush presidency, it is clear that tough is not enough. We need a foreign policy that is both tough—and smart."

Bayh talked about isolating Iran if Tehran continues to pursue nuclear weapons. What if that doesn't work? "There will be consequences ... including the use of force," Bayh declared. He also talked about warning the contending parties in Iraq that they must find a political solution, "or they will cease to have our support."

Bush likes to argue that the war in Iraq is part of the war on terror. Bayh, taking up the challenge, said, "Iraq was not a haven for foreign terrorists before March 2003, but it is now... Iraq was not susceptible to Iranian influence before March 2003, but it is now."

Bush scoffs at the notion that the war in Iraq somehow caused the outbreak of Islamic terrorism. Bayh argues that the war in Iraq has made the problem of terrorism worse and that the United States is not safer.

Bayh concluded his remarks by throwing Rove's challenge back at him: "To Mr. Rove, I say, we are ready. Ready to have this debate any time, any place you'd like to have it." In other words, bring it on!

As Bayh's campaign begins to pick up attention, this debate should get very interesting.