For the best reason of all - he can win. Here's why -
Romney, in effect, would be running as a candidate from three states - Massachusetts, Michigan and Utah.
He is governor of Massachusetts, which borders the quintessential primary state of New Hampshire; he is originally from Michigan, a critical electoral battleground where his late father was governor and is still highly regarded; and Romney's Mormon religion and successful oversight of the 2002 Winter Olympics make him an honorary citizen of Utah.
Massachusetts/New Hampshire, Michigan and Utah - Northeast blue, Upper Midwest heartland and Red State west - distinct regional voting blocs - and Romney has a firm base in all three.
That Romney is a Republican from Massachusetts doesn't hurt him; just the opposite. The state is more conservative than the cartoonish mainstream depiction of it; hence the GOP lock on the Corner Office since 1990. To the extent voters elsewhere see the Bay State as a calcified bastion of Bolshevism, Romney comes across as skilled in somehow getting elected governor.
While voters across the country shifted further right in '04, voters here swung left. Romney took his hits for failing in a major goal, which was to bolster the GOP's anemic presence in the Legislature.
Romney wants to cut the state income tax to 5 percent, as mandated by the voters, and with a rising budget surplus as a cushion. He is being thwarted by a Democratic legislature with a 5-1 advantage over Republicans. Just one example of how conservative voters will see Romney as fighting the good fight against people who won't listen to reason.
That Romney looks like he stepped off the cover of Gentlemen's Quarterly, or the AARP version of it, also doesn't hurt, not since JFK came across better to voters watching the 1960 debates on TV rather than listening on radio.
Another parallel to JFK - Romney can field a formidable army of attractive suggogates - his wife, four sons and their spouses - as he did during his successful campaign for governor in 2002.
In his column this week, Time magazine's Joe Klein wrote that Romney's "demeanor and metabolism are the opposite of John Kerry's - informal, conversational, enthusiastic and speedy." The headline for the column, largely favorable: "The Republican Who Thinks Big on Health Care."
Unlike the Democrats, who have settled on Hillary Clinton as presumptive nominee, the GOP has no obvious front-runner - another dynamic nudging Romney to run. Process of elimination puts him in the top tier - divisions remain raw within the GOP over John McCain, along with doubts about his health; Arnold Schwarzenegger, foreign-born, can't run; Republicans may be unwilling to nominate Rudy Giuliani if Clinton, another New Yorker, is the Democratic nominee; and Bill Frist can't seem to shake questions about health care financial skulduggery.
Potential wild cards - Virginia Senator George Allen, son of the late Washington Redskins head coach and as down to earth as politicians get; and Secretary of State Condoleezza Rice, running as vice president if Dick Cheney resigns due to his health.
My guess is that Romney is sweating Rice's possible presence in the race more than anyone else's, because Rice would draw from two core Democratic constituencies - women and blacks. The opportunity for the party of Lincoln to elect the first black president could be too historic to let pass and the best thing for race relations since, well, Lincoln.
Which is why Romney also makes an appealing vice presidential candidate - running with Rice.
Romney can't wait much longer to announce, certainly not in the week between Christmas and New Year's, the dullest news cycle of the year, or within a week of Christmas, as the holiday season kicks into full gear.
Nor can Romney wait until January, unless he wants to deprive himself of campaign contributions for the 2005 calendar year - all of which gives him about a week to announce.
Why haven't we gotten any hints of a looming announcement? Better not to build it up beforehand and risk the national media covering it as an afterthought when it actually happens - which is usually how the national media covers it.