SIOUX CITY, Iowa — One of the most striking aspects of Fred Thompson’s message in the run-up to his official presidential campaign, which began in this state yesterday, was his commitment to federalism — the principle that decisions about how people live should be made as close as possible to the people themselves, by local or state governments, as opposed to by a federal government hundreds of miles away in Washington, D.C. Rolling along the campaign trail, however, Mr. Thompson seems to have hit the speed bump of political inconvenience.

How else to explain Mr. Thompson’s first major policy proposal of the 2008 campaign, unveiled this morning during a question-and-answer session at the Sioux City Convention Center: that there should be a constitutional amendment banning state judges from interpreting their states’ constitutions as requiring the recognition of same-sex marriages.

“What we’re seeing here is a totally judicial created problem,” Mr. Thompson said of gay marriage. Under an amendment to the constitution that he would propose, he said, “judges could not impose this on the federal or state level, unless a state legislature signs off on it.”

Mr. Thompson’s proposal marked a significant departure from the stance he has held on the issue in the weeks leading up to the campaign. His federalist principles have heretofore prevented him from supporting the Federal Marriage Amendment, which would define marriage in the United States as being restricted to the union of one man and one woman. The formulation would leave no room for state-level decision making. The furthest he’s been willing to go is to say that he would support an amendment preventing one state from being forced to recognize gay marriages legalized in another.

That, however, was nowhere near far enough for many social conservatives. Yesterday, former presidential candidate Gary Bauer, head of the Campaign for Working Families PAC, told me that while there had been “a lot of initial excitement” about Mr. Thompson’s entry into the race among an informal group of about 60 prominent “pro-family” activists over which he presides, the former Tennessee senator’s position on the FMA was a stumbling block preventing the group from cohering around his candidacy. “This group has not been able to agree on anyone after a year of lengthy conversations with the candidates,” Mr. Bauer told me.

While Governor Romney may seem an obvious alternative to Mr. Thompson — he supports the FMA and has generally tried to position himself as the most socially conservative candidate in the race — Mr. Bauer said there was “concern about the sincerity of some of his relatively recent views on some of these issues.” This, he said, has prevented the group from coming to such a consensus on Mr. Romney.

Reached today for his reaction to Mr. Thompson’s new position on gay marriage, Mr. Bauer sounded encouraged, but far from convinced. “This would be a major step in the right direction from what the campaign had suggested earlier, which was a pure federalism approach to the issue,” Mr. Bauer told me. However, he said, “even if a legislature chooses same-sex marriage, how in the world can you have a country where people are married in one state and not in another? The legal mess would be substantial.”

“Some pro-family leaders will want an opportunity to make the case that you should no more allow a legislature to institute gay marriage than allow it to institute polygamy,” Mr. Bauer concluded.

The Thompson campaign insists that its shift on this issue has nothing to do with courting social conservatives. “This is something that he’s been thinking about for a long time, and it’s perfectly in line with his federalist view about the role the federal government should play,” Thompson campaign spokesman Todd Harris told me. Yesterday, however, campaign manager William Lacy acknowledged to me that the campaign was concerned about “a bit of a disconnect” with Mr. Bauer’s group and was working to repair it.

Despite doing some of that work, however, Mr. Thompson has arrived, at least for the time being, at a position unlikely to please anyone.

Mr. Thompson deserves credit for trying so hard to cleave to principle. He could have signed onto the FMA months ago and made his life a lot easier. But, as he put it today, “I’m not going to come down to Iowa or anywhere else, Tennessee, and say your state legislature can’t decide for you on an issue like that ultimately. That’s between you and your state legislature.”

For this new position to make any sense, though, he has to ignore the way the wind is blowing. “I don’t think it [will] ever happen,” Mr. Thompson said. “I think the chances of gay marriage in law passing in any state in this country, by their legislature, is virtually zero.”

On this, Mr. Thompson is simply mistaken. It’s already happened in American’s biggest state, California, where the legislature passed a bill legalizing gay marriage in September of 2005. Governor Schwarzenegger vetoed the bill (as he’s expected to veto a similar measure being sent to him this month), but some future governor almost certainly will sign it. In Connecticut, the legislature passed civil unions in 2006 without any interference from the state courts; it will only be a matter of years before it legalizes gay marriage. In New York, Governor Spitzer got elected promising to introduce a bill legalizing gay marriage; he hasn’t delivered yet, and it may take awhile to bring around the Republican-controlled senate, but the Empire State is another possibility to prove Mr. Thompson wrong.

That there’s political momentum behind the issue is acknowledged even by high-profile opponents of gay marriage, including Princeton professor Robert P. George. “It would be the slow way, rather than the fast way, to same-sex marriage,” Mr. George said of Mr. Thompson’s proposal today. “It’s too hard over the long term,” Mr. George said. As some states passed gay marriage, others would face pressure to go along with the change. Ultimately, Mr. George said, “this is a national question.”

Not to mention a political question — and one that Mr. Romney’s not going to let Mr. Thompson forget in Iowa, where a Polk County judge last week declared that the state law banning same-sex marriage was in violation of the state constitution. That one will be making its way through the state courts for some time.

At the end of the day, the political payoff here simply doesn’t seem worth the damage this shift — not to mention further shifts — will do to Mr. Thompson’s reputation as a principled federalist. If state judges are out of control, that’s a matter state lawmakers and executives can remedy by selecting better judges. In more than 20 states, the people have taken matters into their own hands and passed state-level constitutional amendments defining marriage.

Real federalism is about letting a diverse nation live as one by giving states autonomy — not trying to rig their governing institutions.

rsager@nysun.com