Observing the Tuesday returns, I wrote of Rick Santorum, “He hasn’t had the reach to win in Ohio, Michigan, Florida and elsewhere, or even to win in urban and upscale suburban locales in conservative states. (For example, he lost Montgomery County in Alabama by 10 points to Romney. He lost Jefferson County by five points.) Being the most conservative candidate who can win among the most conservative voters in the most conservative states does not get you the nomination.”

A Right Turn reader wrote to me, wondering “what this means for the conservative wing of the Republican Party going forward.” The reader opined that with changing demographics, the GOP will need to appeal to urban as well as rural voters.

It is certainly the case that Santorum’s electorate contains the most conservative, most religious and most rural constituents in the party. They are also voters who are looking for the most conservative candidate, rather than the most electable.

Every Republican presidential nominee needs such voters to win the White House, but if he only has such voters he will lose badly both in the popular vote and in the electoral college. As we have seen, even within the GOP primary electorate, these are not a majority of voters. Mitt Romney has gotten roughly 3, 472,000 votes. Santorum has gotten about 2,282,000. Aside from Colorado, Santorum hasn’t won any of the states that will be swing states in the fall (New Hampshire, Ohio, Florida, Virginia). This is the reach of the Republican Party’s right flank. It doesn’t extend very far, and it is nowhere near a national governing majority.

To win presidential elections, Republicans need rural and suburban voters; men and women; conservatives and moderates; and religious and not very religious voters.

Consider the latest Gallup poll:

Romney leads Santorum by only 3 points, 34% to 31%, among weekly church attenders, but he leads by 18 points, 35% to 17%, among those who seldom or never attend church.

And these are Republicans. If the GOP writes off all but rural, religious and ultra-conservative voters, it cannot win the White House.

Beyond the core base, the GOP needs some other voters, including independents, Hispanics, single professionals and suburbanites. Look at those Republicans who have won in recent years in non-red states — Sen. Marco Rubio (R-Fla.), New Jersey Gov. Chris Christie, New Mexico Gov. Susana Martinez and Virginia Gov. Bob McDonnell — and you will see some commonalities.

Winning Republicans who are victorious outside of places that are GOP strongholds stress economic issues; talk about upward mobility and school reform; eschew trash-talking the president; and stress that they are opposed to illegal immigration but not immigration or immigrants. They tend toward the wonkish side, but they also exhibit a common touch and use their personal experiences to relate to (and not separate themselves) from ordinary voters. Their techniques and backgrounds differ (e.g. McDonnell has a military background, Christie employs humor, Rubio invokes the immigrant experience), but they manage not to scare voters.

If the GOP is going to keep pace with the changing electorate, the party, as I have argued before, will need to find language and policies that are not off-putting to Hispanics. They will, in the years to come, need to recognize the degree to which gay marriage has won popular acceptance — an issue that transcends gay voters and that puts Republicans at odds with many suburbanites and young voters. (It is noteworthy that Christie smartly shipped that issue out to the voters.) These are long-term propositions, but, if ignored, the issues and demographic groups that care about them will become barriers over time to winning the White House.

For now, however, the Republican Party is in a bit of tug-of-war. The Santorum voters (the most conservative of the base) will deliver for him where they are in the majority, in states such as Alabama, Mississippi and Colorado. But when the race moves out of those uber-conservative enclaves, Romney’s coalition is sufficient to give him the win. Republican voters, a healthy majority of them, don’t want to be stuck with a candidate with the narrowest appeal. They have been following the advice of William F. Buckley Jr., and are choosing the most conservative, electable candidate. (Romney trails President Obama by a average of four points; Santorum by double that.)

There is no guarantee the Republicans will win with Romney, but they will certainly lose with Santorum. If you doubt it, look where he can win and where he can’t.