Mitt Romney squeaked through Michigan's GOP presidential primary this week with a narrow, three-percent win over Rick Santorum. And the allocation of the state's 30 delegates was even tighter — both candidates emerged with 15, leading Santorum's camp to call the race a tie. But the campaign spending race wasn't even close, with Romney, once again, outspending his rivals by a mile. Here, a look at the Republican frontrunner's "huge" financial edge, by the numbers:

$4.3 million
Amount Romney and his super PAC, Restore Our Future, spent on TV and radio ads in Michigan. About $2.3 million of that went to TV ads paid for by Restore Our Future.

$2.3 million
Amount Santorum and his backers spent in the state. Most of the total — $1.3 million — came from the pro-Santorum super PAC, Red White and Blue Fund.

Amount that Priorities USA, a super PAC supporting President Obama, spent on ads attacking Romney

Amount Ron Paul spent in Michigan

Amount the pro-Romney Restore Our Future spent on Tuesday's primary in Arizona, which Romney won handily. His campaign spent nothing.

Amount Santorum spent in Arizona

Dollars Romney spent in Florida for every $1 spent by Newt Gingrich, who, after a victory in the South Carolina primary, was then Romney's biggest rival

Dollars Romney spent for every $1 Gingrich spent in Iowa, where Romney and his allies "buried" the former House speaker with negative ads

$38 million
Total campaign spending by Romney and his "pet" PAC to date

$9.7 million
Total spent by Newt Gingrich and the super PAC supporting him

$6 million
Total spent to date by Santorum and his super PAC, the Red White and Blue Fund

$6.5 million
Amount Romney raised in January

$32 million
Amount Barack Obama raised in January 2008, when he was locked in a Democratic primary battle with Hillary Clinton

Sources: Hot Air, Politico, Telegraph, Wash. Post