Remember way back when Romney led Santorum by 16 points in Gallup’s national tracking poll? That was … four days ago. Today: Romney 32, Santorum 30, Gingrich 16. Mitt’s lucky that there’s a nice long break between Santorum’s three wins in the midwest last week and the next key primaries in Arizona and Michigan. If there wasn’t, I don’t know if even a flurry of negative ads from the Romney Super PAC death star would be enough to snuff Santorum’s momentum in time.

Santorum had been planning a slow-and-steady-wins-the-race plod through the primaries, but according to Politico, he’s now thinking about knockout blows:

A potential path to breaking open the race against Romney, they say, could run through Michigan’s Feb. 28 election and Ohio’s Super Tuesday vote on March 6 — two Rust Belt primaries in which they believe Santorum’s working-class background and manufacturing-heavy message will resonate. (Arizona’s winner-take-all primary, also on Feb. 28, looks less inviting.)

The privately held hope in the Santorum camp is that beating Romney in his native state of Michigan or in the ultimate general election battleground of Ohio would discredit, on a grand scale, the on-and-off Republican front-runner and make the other candidates in the race irrelevant in the remaining contests.

“If we can get it to a two-person race, I feel very confident that we will be the nominee,” said Santorum strategist John Brabender, who explained that the campaign is assessing where to play based on the number of delegates at stake and the cost of competing in each state.

They hadn’t made any decisions on what to do as of this morning but those new ARG and PPP polls out of Michigan will likely force their hand. Truth be told, though, I think this is less a story about “the Santorum surge” than “the Romney collapse.” Feast your eyes on these national numbers from Pew, which has Santorum suddenly up by two after trailing by double digits a month ago:

Three months ago, a slim majority (53%) of Republican and Republican-leaning voters said Mitt Romney was a strong conservative. Today, 42% see him this way, while the number who say he is not a strong conservative has jumped from 33% to 50%…

Fewer Republican voters today think Romney has been consistent as well. By a 48% to 39% margin, more Republicans say Romney does not take consistent positions on the issues. In November, 47% felt he was consistent and just 33% said he was not…

Barack Obama now holds an eight-point lead over Mitt Romney in a general election matchup, and he has gained significant ground among independent voters. A month ago, 40% of independents said they would back Obama over Romney – today 51% say they would, while the number expressing support for Romney has slipped from 50% to 42%.

Romney’s downturn among indies is simply brutal:

Head to head, Obama now leads Santorum by 10 points and Romney by eight, leading David Frum to wonder what’s left of Mitt’s “electability” argument to the base. Now you see why Santorum’s thinking about going all in on Michigan and Ohio: In theory he could knock Romney into a death spiral where each new swing-state defeat erodes a little bit more of the base’s confidence in his electability, which in turn makes future swing-state defeats more likely. Given that Romney’s gotten off lightly so far in terms of attack ads aimed at him, though, I’m not sure how to account for his downturn among independents. Some of it must be due to the debates — remember how effective Santorum’s RomneyCare attacks were? — but the debates didn’t stop Mitt from a landslide win in Florida. Some of it must be from conservative talk radio talking up Santorum and talking down Romney, but I’d expect to see more movement among grassroots conservatives in that case than among independents. I wonder, actually, if Gingrich’s Bain attacks, coupled with Romney’s gaffes about how he likes being able to fire people and isn’t concerned with the very poor, were more effective with middle-class independents than we thought. Note the last line in that Pew graphic I posted above; his net on the question of whether he understands the needs of people like you more than doubled from -14 to a disastrous -29. I don’t know how he turns that around, especially against a candidate with blue-collar appeal like Santorum. Presumably he’ll just attack, attack, attack until he’s once again the most electable candidate in the field, even if increasingly he isn’t very electable at all.

Update: Annnnnnnd here we go. The death star prepares to fire:

Mitt Romney is getting some heavy air support in Michigan — the state where he was born and raised — as the “super PAC” supporting him invests almost $500,000 on television ads there.

According to someone who tracks Republican media spending, Restore Our Future has committed just over $470,000 for commercials starting Tuesday and set to run through Feb. 20. That marks the group’s largest purchase yet in Michigan, where it has already spent more than $700,000 on ads.

Supposedly their first ad buys will target … Gingrich. Why?