The immigration reform debate continues to defy stereotypes and conventional wisdom. In just one day we saw that in abundance.

Not a single right-leaning think tank rose in defense of Heritage’s anti-immigration study. The American Enterprise Institute, the Cato Institute, Manhattan Institute, the Competitive Enterprise Institute, the Kemp Foundation and other pro-free market entities are on the other side. (The Post’s analysis detailing all the specific methodological flaws in this regard is entirely in sync with the Heritage critics.)

So most of the intellectual heft on the right is firmly on the pro-immigration side. Polling shows most Republicans are favorably disposed toward immigration reform with conditions like those set out in the Gang of Eight’s plan.

That is not to say everyone on the right thinks the bill is perfect. To the contrary, conservative economists on a press call yesterday skewering the Heritage study urged expansion of the guest-worker program and tightening of eligibility restrictions for federal benefits for those legalized. Yuval Levin has some suggestions as well (although I think there is contrary evidence concerning immigrants’ impact on low wage-earners). But these are hardly fundamental objections.

And, of course, no set of facts and no bill will satisfy those whose minds are already made up and whose readership, fundraising or audience demands an anti-immigration line.

But then it isn’t really fair to say the “right” opposes the Gang of Eight plan or to remark on “conservative opposition to the bill.” The opponents are one sliver of the right, and not a segment that has come up with reasoned analysis for its side. Saying the bill could be better is not the same as saying it would be worse than the current situation of de facto amnesty, non-enforcement of the law, unpaid taxes (aside from sales and other consumption-based levies), exploitation and non-assimilation.

Immigration exclusionists’ political analysis is just as bad. Well, even with a whole bunch more Hispanic votes Mitt Romney wouldn’t have won, they say. That would be an effective argument, I guess, if the GOP were planning to run Mitt Romney in every future presidential election. It might make sense if one discounted the impact that immigration reform has on the perception of the GOP by other minority groups and by moderate voters more generally. Unfortunately, the immigration opponents’ political thinking is as static and, therefore, as flawed as their economic analysis.

But let’s get real. About 350,000 votes in a few swing states were the difference between electoral defeat and victory in the 2012 presidential race. Does any Republican candidate eyeing the presidency not want to improve the party’s standing with minorities? Immigration-reform proponents such as Sen. Marco Rubio (R-Fla.) aren’t basing their policy on political calculations. But, even if they were, reformers are generally in favor of a whole bunch of improvements and reforms in the Republican Party. Immigration reform is necessary but hardly sufficient for Republicans to remain a national party.

Finally, I was struck yesterday by how intensely negative is the perspective of immigration reformers. (The government will never enforce the law. Immigrants will never get off the dole. Immigrants will never rise from poverty. More immigrants make us poorer. There are only so many jobs to be had. Immigrants will never assimilate. Republicans can never win these voters over.) Skepticism is fine, but this is not the spirit of modern conservatism, nor, as economist Doug Holtz-Eakin pointed out in yesterday’s call, does it reflect belief in the American dream. It surely doesn’t comport with supply-side economics.

Moreover, if the GOP can never appeal to minorities then it’s over. The minority segment of the population will continue to grow; there aren’t enough voters left over for the GOP to win national elections with high turnout. Nor is it morally defensible to have a party that only serves the interests of and relies on the support of white, native-born voters. Conservatism is supposed to be about eternal values (freedom, opportunity) that know no racial, ethnic or religious divide. If that’s not true , then it’s not a governing philosophy for 21st century America.

UPDATEDiana Furchtgott-Roth, a senior fellow at the Manhattan Institute, is the latest to detail Heritage’s gross errors. She concludes: “The report refers to the legalization process as ‘amnesty,’ deliberately overlooking the penalties required to be paid by undocumented workers in order to receive legal status. The term ‘amnesty’ is a misreading of the immigration bill, inserted to prevent the bill from becoming law. The report assumes all will choose naturalization and all will be on welfare. … The report assumes that immigrants stay poor, contrary to data on income mobility from the U.S. Department of the Treasury. … By neglecting benefits of legal immigration, the Heritage report presents a misleading view of reform legislation under discussion in Congress.”