For months, the presidential campaign of former Tennessee Sen. Fred Thompson has been a kind of Zen koan: How long can a campaign go on until it becomes a campaign?

Too long, said most political pundits in the days after Thompson announced his candidacy on the Jay Leno show.  Thompson should have formalized his bid in July, they said, at the peak of his novelty, before the shine was rubbed off by dissension among his campaign staff, before the decidedly mild response to his fundraising efforts, and before the spreading uncertainty as to what, exactly, he brings to the fight for the Republican nomination.

Whatever it is, it’s not a record of executive accomplishment that might predict presidential competence.  That would be Rudy Giuliani and Mitt Romney.  It’s not the purity of his conservative convictions.  That’s Sam Brownback or maybe Mike Huckabee.  He doesn’t have an inspiring personal story like John McCain, or an ideological niche like Tom Tancredo or Ron Paul.  His manner is engaging, but not more engaging than Huckabee’s.*

All of which is why Thompson’s entry into the presidential race may have come not too late, as the pundits have been saying, but too early.

Whether in July or September, Thompson comes into the race as one of a scrum, battling to differentiate himself from the others.  Come the next debate, he will be the tallest, but otherwise indistinguishable from the rest: hoping to finish a respectable second or third to Giuliani in Iowa or New Hampshire or to avoid being overtaken by the Huckabee surge or the McCain resurgence.

True, had Thompson waited, he would have risked that one of the others might lock up the contest before the former Tennessee senator could even get in.  Whatever the final sequence of primaries turns out to be, anyone who wins all of them or several of them convincingly may emerge with an insurmountable lead.  But if any of them is that strong, maybe Thompson’s candidacy was doomed before he even declared.

But an equally likely scenario might have offered Thompson an opening uniquely suited to what he brings to the table.  At least as likely as a sweep is a stalemate.  Romney could do well in Iowa and New Hampshire, Giuliani in Florida, Huckabee in South Carolina, and McCain in Michigan, which he won in 2000.  The contenders might emerge from the earliest primaries clumped together, and looking to differentiate themselves and to knock from contention opponents vying for the same segment of voters.

It is often at such times that campaigns turn negative.  Liberal-leaning clips from Romney’s Massachusetts campaigns might become more prominent, as might headlines recalling Giuliani’s domestic difficulties, McCain’s 2000 criticism of evangelical Christian leaders and McCain’s support for campaign finance legislation, tobacco regulation, and even his intervention with bank regulators on behalf of Charles Keating, an S&L mogul later convicted of fraud.  Facing a series of crowded and closely-fought primaries, each candidate would seek to energize highly-motivated blocs by demonstrating the purity of his pro-life, anti-immigration, or pro-tax-cut fervor and digging up past examples, no matter how obscure or how long ago, of his opponents’ apostasy.

In other words, things could get ugly.

Into that breach could have stepped Fred Thompson.  The laid-back demeanor that now raises suspicions of insufficient motivation would, in that fevered environment, have looked like centeredness and a welcome absence of overweening ambition.  His vague positions on issues would have looked like the moderation that general election voters often value.  He would have come, to borrow from Matthew, not with a sword, but to bring peace.

Who knows?  Maybe Thompson will be able to maintain his avuncular geniality through the close combat of the next several months.  Maybe he can continue to project the aura of confident authority that he has developed on TV and in the movies.  Maybe his young and glamorous wife, and the even younger and more glamorous young women he dated before his remarriage, will add a bit of zest to the borderline codgery persona he has cultivated.

Maybe, in other words, Fred Thompson will fight through the primaries and break out of the scrum.

But he faces longer odds than he would have if he had bided his time.

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*  Rudy, Mitt, Sam, Mike, Tom, Ron?  Are these men friends of ours?  Is that why we know them by these nicknames?  If FDR were running today would he be “Frank”?  Would Hoover be Herb?  William McKinley Bill?