Three polls showed how tight the race is between Romney, the former Massachusetts governor, and Santorum, a former U.S. senator from Pennsylvania, the Detroit Free Press reported.
The primary is Tuesday.
A Mitchell Research/Rosetta Stone poll conducted for the Michigan Information & Research Service indicated Santorum topped Romney, 37 percent to 35 percent, with former House Speaker Newt Gingrich collecting 9 percent and U.S. Rep. Ron Paul of Texas receiving 8 percent. The survey of 420 likely GOP primary voters was conducted Monday and has a margin of error of 4.7 percentage points.
Public Policy Polling had Romney ahead of Santorum 39 percent to 37 percent, with 13 percent saying they favored Paul and 9 percent saying they backed Gingrich. The survey of 421 likely Republican primary voters was conducted Sunday. The margin of error is 4.8 percentage points.
A poll by Foster McCollum White & Associates indicated Romney held a 39-31 lead over Santorum, with Gingrich and Paul tied at 9 percent. The poll was conducted Thursday among 2,416 likely Republican primary voters. The margin of error is 2.1 percentage points.