Michigan primary goes down to the wire Republican presidential hopeful Mitt Romney (L) is expected to best his nearest rival, Rick Santorum, in the delegate count in Tuesday's Michigan and Arizona primaries. DETROIT, Feb. 28 (UPI) -- Republican presidential rivals Mitt Romney and Rick Santorum slashed at each other ahead of Tuesday's Michigan primary, now too close to call. The contest in his home state is seen as crucial to Romney and his claim of the front-runner's mantle. Meanwhile, polls show Romney pulling away in Arizona where Tuesday's other primary goes down. The Washington Post said five polls conducted during the weekend indicate Romney and Santorum are within 4 percentage points of each other -- Romney leads in three of the polls, Santorum in two, but the margins are so close as to be statistically insignificant. The Post did not report the methodology of the polls. Despite the closeness of the Michigan race, the Post said Romney was expected to win about three times as many convention delegates as Santorum Tuesday. Arizona is a winner-take-all primary. Michigan's 30 delegates are allotted proportionately to the primary winner in each of the state's 14 congressional districts. Arizona's winner picks up all of its 29 delegates. The Post said Romney was expected to garner 45 delegates from both contests, with Santorum picking up about 15. Rivals New Gingrich and Ron Paul were not expected to win any delegates, and did not seriously campaign in the two states. In Arizona, a Public Policy Poll released Monday indicated 43 percent of likely voters would vote for Romney, 26 percent for Santorum, 18 percent for Newt Gingrich and 11 percent for Ron Paul, The Daily Beast reported. The news Web site said Romney has made inroads among Santorum loyalists, including Tea Party members, evangelicals, senior citizens and the "very conservative," an automated telephone poll of 515 likely Republican voters indicated. The Daily Beast gave no other details of the polling. Romney and Santorum were shooting fireballs at each other. Romney, the former Massachusetts governor, blasted Santorum's use of robocalls urging Democrats, who can vote GOP in Michigan, to vote for Santorum. "I know why [President] Obama doesn't want me to face him but I just think it's outrageous and a terrible dirty trick at the last hour, by the way, late in the afternoon on the day before the election, maybe hoping no one would notice, they start sending out calls to Democrats, union members telling them to go into the Republican primary and vote against Mitt Romney," Romney told Fox News. "This is a new low for his campaign and that's saying something," he added. Santorum, a former U.S. senator from Pennsylvania, told Fox News Monday night he's just trying to attract the Democratic voters he'll need in November. "When he runs a robocall of my voice from four years ago saying good things about him, that's not a low moment, and when I run a call basically saying, calling Democrats that are eligible to vote here, to vote for us, that's a low?" he said.