While Rick Santorum courts the blue-collar vote in Michigan, he’s already looking forward to at least one Super Tuesday state — Ohio.  He has spent quite a bit of time in this Rust Belt swing state, and according to the latest Rasmussen poll, that investment has paid off handsomely.  Santorum now leads Romney by eighteen, 42/24:

Former Pennsylvania Senator Rick Santorum continues to ride his polling momentum into Ohio where he leads Mitt Romney by nearly two-to-one in the first Rasmussen Reports survey of Republicans in the state.

The new statewide telephone survey of Likely Republican Primary voters shows Santorum picking up 42% of the vote to Romney’s 24%. Former House Speaker Newt Gingrich draws 13% support, while Texas Congressman Ron Paul picks up 10%. Three percent (3%) prefer some other candidate, and eight percent (8%) are undecided.

Santorum leads Romney by an even bigger margin – 58% to 30% – when the race is down to a one-on-one matchup in Ohio. Romney leads Gingrich 46% to 37% in a two-man race and Paul by a 58% to 26% margin.

The problem for Romney in Ohio mirrors that in Michigan, which is that Santorum’s pitch resonates more with the blue-collar workers that populate the Rust Belt. In fact, Newt Gingrich leads among those earning under $20K a year, 28/19 over Romney, but Santorum wins all other income demographics by pluralities below $75K, and by majorities above $75K.  He also wins every age demo by a plurality, although the 18-39 group only by two points over Romney, 26/24.

The further problem for Romney is that Santorum’s perceived strength in a general election now nearly matches that among Ohio primary voters, 35/34.  Among independents, Santorum actually surpasses Romney on general-election strength, 35/26, among independents.  On the main question, independents back Santorum over Romney 37/19, which gives a little more credibility for the argument for Santorum’s strengths.

There is one big red flag for Santorum, however.  Among those who have already cast their ballots in early voting, Romney leads by seventeen, 40/23.  Depending on how many have already voted, that might put Santorum in a hole that could be significant by the time Romney starts paying attention in Ohio.

Update: Slate’s Dave Weigel says that Santorum has toned down the focus on social-conservative issues the past few weeks:

In the final debate before the New Hampshire primary, when he was asked if he’d be a “gay rights leader”—a pretty blunt trick question—Santorum said he’d “be a voice in speaking out for making sure that every person in America, gay or straight, is treated with respect and dignity and has the equality of opportunity.” If his son told him he was gay, “I would love him as much as I did the second before he said it.” In two new ads, his social conservatism is mentioned only in a long rundown of other reasons to vote for him. One mentions that he was “one of the top 25 evangelicals in America,” according to Time, but the point is left out there, context-free.

The result of all this: polls showing Santorum as an electable national candidate. The strategists who worked against Santorum in 2006 are amused. He gave them length after length of rope, they hung him with it, and essentially, he hasn’t changed. He still holds onto his criticism of homosexuality, for example—that it stems from the rise of the welfare state and loose morals. They have destroyed the American ideal of one-income households. Sex is meant to be a procreation-only pursuit, and they’ve ruined that, too. …

How does Mitt Romney take advantage of that? He hasn’t tried yet. His argument against Rick Santorum is all about the former senator’s résumé, and support for earmarks—stuff  libertarians care about, nothing cultural. The digging into Santorum’s theories about contraception has only just begun. Since he’s risen in the polls, he’s tried to genericize that issue, too, attacking a contraception mandate as the “government trying to control your life,” not as some battle in the culture war. How long can this new Santorum keep that up?

The February 22nd debate might be the first test of that question.