Santorum, Romney vie for the lead ahead of key contests Republican presidential contender Rick Santorum has been riding a wave of momentum since his three primary and caucus victories earlier this month, and the latest Gallup daily tracking poll suggests the former senator is gaining popularity among Republicans nationwide. Santorum's newfound popularity is coming at a critical juncture, with "Super Tuesday" -- the day 10 states hold their nominating contests -- just two weeks away. Within the next two weeks, however, the state of the race could once again change dramatically. The four remaining Republican hopefuls are set to debate in Arizona Wedneday, a potentially game changing event ahead of the February 28 contests in Arizona and Michigan. And ahead of Super Tuesday, the candidates -- particularly former Massachusetts Gov. Mitt Romney -- are sure to draw large sums from their campaign war chests to launch more blistering attacks at one another. Gallup's daily tracking poll of registered Republican voters now shows Santorum leading with 36 percent support. Romney comes in second with 26 percent, giving Santorum his largest lead in the national poll to date. Former House Speaker Newt Gingrich takes 13 percent, and Rep. Ron Paul wins 11 percent. Santorum's standing in the Gallup daily tracking poll began rising after he swept the February 7 nominating contests in Missouri, Minnesota and Colorado. Since then, a few polls have shown Santorum leading in Michigan -- the state where Romney was born and raised. Along with Arizona, Michigan holds its Republican nominating contest on February 28. A loss in Michigan would be a severe blow for Romney, given the expectations set for him in his "home state." Complete 2012 campaign coverage 2012 election results The most recent polls suggest Romney could be closing in on Santorum in Michigan. A Mitchell/Rosetta Stone poll of Michigan Republican voters conducted Monday showed Santorum with a slight, 2-point lead over Romney -- that's within the poll's margin of error. It's worth noting that the one-day Mitchell poll was conducted via robocalling, which is somewhat controversial in the polling field. Another poll released this week from Public Policy Polling (PPP), a Democratic firm, also shows Santorum in a statistical tie with Romney, leading just 37 percent to 33 percent. Both PPP and Mitchell released polls earlier this month that gave Santorum a stronger lead. Polls in Arizona show Romney with the lead there. If Romney really wants to catch up to Santorum in Michigan, he'll have to convince voters there's more to his candidacy than the argument that he's the most electable -- a new USA Today/ Gallup survey, conducted February 16-19, shows that more than half of Americans already think Romney's the most electable GOP candidate. With that in mind, Romney has been busy hitting the campaign trail in Michigan, taking a more personal tone. He's holding a town hall at a manufacturing plant today, while his wife Anne Romney hosts her own events in Battle Creek and Hudsonville, Michigan. How Romney can beat Santorum in Michigan Gingrich backer willing to give $100M Mitt Romney and his surrogates: It's complicated Romney has also stepped up his attacks on Santorum. On Monday, he accused the former senator of making a major contribution to reckless Republican spending, helping the GOP "spend like Democrats," for voting repeatedly to raise the debt limit while he was in Congress. Romney will seek to hit on his personal ties to Michigan and Santorum's flaws in Wednesday's debate. Santorum, meanwhile, should aim to appear presidential in the debate, to build up his own electability argument. As he seeks frontrunner status, Santorum has been sharpening his rhetoric against Mr. Obama on the campaign trail, painting a picture of a president out of touch. However, Santorum will also have to fend off questions about some controversial remarks he's made and possibly some recent campaign gaffes -- such as his campaign surrogate's remarks over the weekend (later retracted) about President Obama's "radical Islamic policies." Today, Santorum is campaigning in Phoenix. Santorum and his rivals are expected to stay aggressive on the airwaves as well as on the campaign trail. Newly-released financial reports show that Romney raised $6.5 million last month, while Santorum and Paul both raised $4.5 million and Gingrich brought in $5.6 million. Romney has $7.7 million in cash on hand -- more than the other candidates combined -- but his campaign has been spending cash twice as fast as it's bringing it in. Romney's negative campaign against Santorum will of course be buttressed by spending from the pro-Romney Super PAC Restore Our Future. Paul, meanwhile, is also launching a negative ad against Santorum, calling the former senator a "fake" fiscal conservative.