Fred Thompson has stepped immediately into the firing line as he tries to rally conservative Republicans to embrace his latecomer presidential campaign. Rival campaigns have already prepared thick dossiers of "opposition research" chronicling the former Tennessee senator's zigzags on such key issues as abortion rights, immigration, a gay marriage ban, and campaign finance reform.
Thompson spent months testing the waters and deciding whether to get into the race for the Republican presidential nomination, giving the other GOP campaigns plenty of time to prepare their responses to his candidacy the moment he made his unorthodox entry on "The Tonight Show" on Wednesday night.
The other campaigns have hinted at some of the tactics they will use. At the Republican debate in New Hampshire on Wednesday night, for example, Senator John McCain of Arizona said of Thompson's absence: "Maybe we're past his bedtime." That feeds into the charges that Thompson, a McCain ally while in the Senate from 1994 to 2002, is lazy.
How he responds to the criticisms, in the form of media scrutiny as well as sniping from rival candidates, will be critical to his viability in coming months.
"He's going to go through the same process we went through months ago, meaning there will be a barrage of questions," said an aide to Rudy Giuliani, former mayor of New York City. "Everything that's a potential liability gets thrown at you when people are really paying attention and there is less time now to recover from it."
Giuliani and former Massachusetts governor Mitt Romney came under fire earlier this year for the moderate positions they took while they held office in liberal states, and both have tacked to the right on core issues after they became presidential candidates.
Karen Hanretty, Thompson's spokeswoman, said the potential liability for Thompson over his positions on issues is different from the criticisms leveled by conservatives at Giuliani and Romney.
"Fred Thompson has a couple of votes pertaining to amendments, which really go back to the notion of federalism and what belongs to the states and what belongs to the federal government," she said. "He's very consistent in a grounded philosophy of federalism - that the federal government should not be making decisions that belong at the state level."
Thompson's opposition to a national ban on gay marriage is troubling to many religious conservatives, but Hanretty said Thompson believes the federal government should not impose a national standard and should leave such issues to the states.
During his Senate campaigns in the 1990s, Thompson said he supported Roe v. Wade, the Supreme Court decision that legalized abortion. But Hanretty said he "had a very solid prolife voting record all eight years he was in office." Earlier this year, Thompson described himself as "prolife." Romney had a similar conversion while he was governor of Massachusetts.
On immigration, Thompson was one of six senators who voted against a 1995 amendment that would have prohibited illegal immigrants from receiving federal benefits except for a few narrow exceptions. Hanretty said Thompson voted against it because it didn't go far enough.
Another potential hazard for Thompson is his career as a Washington lobbyist. A Romney campaign aide said Thompson's experience as a lobbyist for some controversial clients will make it difficult for him to cast himself as a "Washington outsider" in the race, as he has sought to do in his recent appearances. Hanretty responded that lobbying was a minor part of Thompson's career.
His enthusiastic support for campaign finance reform is certain to antagonize many conservatives.
Thompson was the second Republican sponsor, after McCain, of the McCain-Feingold campaign finance reform law, a portion of which was struck down on free speech grounds by the Supreme Court this year.
"He recognizes there were unintended consequences of the McCain-Feingold legislation, and he'd like to revisit the issue," Hanretty said. For instance, she said, Thompson favors more disclosure about the financing of groups that operate independently of campaigns and political parties.
Thompson's comparatively late start also leaves him struggling to cobble together uncommitted GOP contributors, endorsements, and operatives.
Ralph Reed, a Republican strategist who is unaligned in the GOP contest, said Thompson cannot expect to lock up the wholesale support of uncommitted social conservatives at this point.
"With any constituency this large and diverse and with so many candidates competing for their affection, it's unlikely that they will be corralled by a single candidate, and with a late entry it's going to be hard to get all these people," Reed said.
Nevertheless, he said, Thompson enters a "highly fluid race with no sort of presumptive nominee. You could make an argument that we have not seen such a situation in the party since 1964."
"There have always been scares and near-death experiences [for candidacies] but there was always someone who was the presumptive nominee," said Reed, a former executive director of the Christian Coalition and a key player in President Bush's victories in 2000 and 2004.
The website RealClearPolitics, which tracks polling data, indicated Thompson, before his announcement, in second place, about 11 points behind Giuliani in an average of six independent national surveys since Aug. 7, slightly ahead of Romney and McCain.
Thompson also faces organizational challenges, particularly in the early states, such as Iowa and New Hampshire, where a ground game is essential and most activists have signed on with other campaigns. Yesterday, Thompson's campaign announced the hiring of a pair of operatives in Iowa, and last week, the Iowa Republican Party's top organizer, Kristen Fuzer, joined the Thompson campaign.
Yesterday in New Hampshire, Thompson supporter Daniel Hughes, a former state representative from New Castle and a key organizer for the Ronald Reagan Granite State campaign of 1980, was surveying storefronts along the streets of downtown Manchester in a search for a Thompson campaign headquarters - just four months before the state's first-in-the-nation primary.
Globe correspondent James W. Pindell contributed to this report.