By Carl Leubsdorf

The Dallas Morning News

As the Republican presidential race finally revs up, it’s important to separate the significant from the transitory.

For example, Mike Huckabee’s decision to bypass the GOP race is more important than Mitch Daniels’ similar decision because the former Arkansas governor had substantial strength in Iowa, where he won the crucial opening caucuses four years ago.

And former House Speaker Newt Gingrich is right when he says his enthusiastic reception in 17 Iowa appearances may matter more than the Washington punditocracy’s roasting of his most recent verbal gaffes.

Here are some guidelines to the race that will produce President Obama’s GOP challenger:

—Iowa and New Hampshire matter — a lot. To be a significant factor, any candidate almost certainly has to win one of them. Huckabee was the first Iowa GOP winner to lose the nomination in 20 years. John McCain’s New Hampshire victories in 2000 and 2008 overcame poor Iowa showings.

Midwestern candidates such as the two Minnesotans, former Gov. Tim Pawlenty and Rep. Michele Bachmann, benefit from Huckabee’s withdrawal, but they almost certainly have to win Iowa. Ditto for Texas Rep. Ron Paul, who needs to show he can expand his enthusiastic libertarian base, and the other aspirants wooing GOP social conservatives: Gingrich, former Pennsylvania Sen. Rick Santorum, former restaurant executive Herman Cain and, if she runs, former Alaska Gov. Sarah Palin.

The Aug. 13 Iowa straw poll will establish the initial pecking order.

Similarly, New Hampshire is a must for former Massachusetts Gov. Mitt Romney, and it’s where former Utah Gov. Jon Huntsman needs to take advantage of independent voters to upset Romney.

History says any candidate who wins both states will be the nominee.

—So does South Carolina. Every South Carolina winner has won the GOP nomination since Ronald Reagan in 1980. But all first won Iowa or New Hampshire. The state GOP’s strong religious conservative base could make it hard for Romney — or Huntsman — to emulate McCain’s victory, unless more than one more conservative rival survives Iowa and New Hampshire.

It’s too early to judge the strongest Republican candidate. Speculation that establishment figures such as Huntsman or Romney, who have been governors, would be strongest because they could appeal to independents may be disproven when the true front-runner emerges.

—Running for president is hard. And it’s gotten harder in this era of 24-hour cable news and internet coverage. Gingrich’s rough rollout was a reminder it’s unlike seeking any other office. That gives a repeat aspirant such as Romney some advantage.

—Debates matter — a lot. Since most GOP hopefuls are not well known, how they present themselves and respond to one another in televised debates starting June 13 in New Hampshire will help many Republicans decide who would fare best against Obama.

—No national Republican “they” will ultimately pick the nominee. Party leaders lost that power when primaries and caucuses became the venue for choosing most convention delegates.

In an unlikely deadlock, the candidates themselves would resolve matters, rather than cede power to non-candidates.

—Speculation about alternative candidates is inevitable, but rarely productive. Many Republicans would like former Florida Gov. Jeb Bush or New Jersey Gov. Chris Christie to run. Both say no.

It’s like 1992, when top Democrats bypassed the race, leaving a seemingly weak field against the first President Bush. But Bill Clinton emerged as an excellent candidate, and economic weakness sapped Bush’s support.

—Incumbent presidents can be beaten — but it’s hard. In the past century, five incumbents lost. William Howard Taft in 1912, Herbert Hoover in 1932 and Bush in 1992 lost after their party held office at least three consecutive terms. In 1976, Gerald Ford was an unelected president after the Watergate scandal forced Richard Nixon’s resignation.

In 1980, Jimmy Carter became the only president since 1892 to lose four years after his party regained the White House, and his election was something of a fluke.

If unemployment stays well over 8 percent, and a majority of the public still considers the country headed in the wrong direction, Obama will be vulnerable.

But GOP hopefuls need to avoid painting themselves into too conservative a corner in wooing Republicans. And portents still suggest Obama is the likeliest winner.

Carl P. Leubsdorf is a syndicated columnist and the former Washington bureau chief of the Dallas Morning News. Readers may write to him via email at: carl.p.leubsdorf@gmail.com.