Evan McMorris-Santoro January 1, 2012, 5:22 PM

ATLANTIC, IOWA — Rick Santorum really has arrived, it seems. After meeting with voters in a diner here Sunday, Mitt Romney hosted a rare press conference where he was more than happy to take Santorum on in the way he has other surging candidates in the past.

It’s a sign that Santorum’s surging poll numbers have caught the attention of Romney, who’s pushing hard to win here in Iowa, a state he wasn’t able to win during his 2008 White House run. Anecdotal evidence suggests some voters are choosing between the two men — three undecided Iowans I talked to before Romney arrived said Santorum and Romney were on their short lists.

With Newt Gingrich, Rick Perry and Michele Bachmann — candidates who have in the past challenged Romney for dominance in Iowa — falling off and Ron Paul’s surge appearing to be losing steam, it’s possible that the homestretch here in the Hawkeye State could be a battle between Santorum and Romney.

Here’s what that sounds like.

Asked what he’d say to voters choosing between him and Santorum, Romney said he’d rather not talk about others’ records, preferring to stay focused on his own. He then not-so-subtly reminded the reporters present who Santorum backed for the nomination in 2008.

“Senator Santorum was kind enough to endorse me last time around, I appreciate that,” Romney said. “We’ve been friends.”

Then Romney turned the knife.

“I can tell you that our backgrounds are quite different,” he said. “Like Speaker Gingrich, Senator Santorum spent his career in government, in Washington. There’s nothing wrong with that, but it’s a very different background than I have.”

I think the people in this country recognize that with our economy as the major issue we face right now, that it would be helpful to have someone who understands the economy firsthand and has spent the bulk of his career working in the private sector.

“Senator Santorum’s a good guy, he’s worked hard. I wouldn’t be surprised if we see him do well on Tuesday and I think a good deal of him,” Romney concluded.

So this is not the level of attack that from Romney that, say, Gingrich got when he was at the top of the heap. But it shows that Romney is ready to engage Santorum, something he might have to do more if he wants to win this thing.

2012, 2012 Presidential Primaries, GOP, GOP-Pres, Iowa, Iowa Caucuses, Mitt Romney, Rick Santorum