Thompson's Politics Much Like McCain's

To be sure, Thompson and McCain have some significant differences on policy. McCain, for example, opposed Bush's income-tax cut proposals in 2001, infuriating the party's base. Thompson backed them. The Tennessee senator did not join some of McCain's bills with Democrats, such as his effort to create a "patients bill of rights."

And if McCain is acknowledged to be an energetic legislator, Thompson had few signature accomplishments. At times, he seemed not to enjoy politics and sometimes griped about the long hours in the Senate. When he decided against running for reelection in 2002, he told the Tennessean newspaper, "All kinds of opportunities are out there . . . without having someone else determine your schedule every day, and not have to sit around at 10 o'clock at night over some Senate resolution that shouldn't be on the floor anyway."

Those kinds of complaints have led some to quietly question whether Thompson has the drive to run for president. Rep. Mark Souder (R-Ind.) said, "Not getting in early raises questions about his passion."

His supporters brush aside such concerns, noting Thompson's victories in two Senate campaigns and his years as chairman of the Governmental Affairs Committee. "Fred Thompson is a slow-talking, slow-moving Southern guy," said Burson Snyder, who served as Thompson's spokeswoman. But "there were a lot of nights where he was burning the midnight oil."

Now, Thompson appears to be moving gradually toward answering the question he posed when he was mentioned as a potential 2000 White House contender.

"Why would one want to run for president? That's the real question," he said. "Not, why does one not run for president?"

Political researcher Zachary A. Goldfarb, staff writer Michael D. Shear and washingtonpost.com researcher Derek Willis contributed to this report.