On the eve of the final Republican presidential debate before primaries in Arizona and Michigan, as well as the 10 Super Tuesday states, a new survey indicates that Rick Santorum may be closing the gap with Mitt Romney in the Grand Canyon State.

According to a CNN/Time/ORC International poll released Tuesday, 36% of people likely to vote in Arizona's February 28th GOP presidential primary say they're backing Romney as their party's nominee, with 32% supporting Santorum. The former Massachusetts governor's four point margin over the former senator from Pennsylvania is within the survey's sampling error, meaning they are basically tied for the top spot.

The poll indicates that 18% are backing former House Speaker Newt Gingrich, with 6% supporting Rep. Ron Paul of Texas and 6% unsure. Surveys conducted earlier this year by other organizations indicated Romney with a larger lead over the rest of the field of candidates.

Santorum surged in state and national polling after sweeping the February 7th contests in Colorado, Minnesota and Missouri.

The four major GOP White House hopefuls will face off Wednesday at a CNN/Republican Party of Arizona debate in Mesa, the first GOP showdown in nearly a month.

The CNN/Time/ORC poll indicates that roughly a third of all likely voters say that they could change their minds between now and February 28, emphasizing the importance of CNN's debate as well as the final week of campaigning.

"Arizona Republicans display many of the same ideological divisions that drove the results in earlier primaries and caucuses," says CNN Polling Director Keating Holland. "Santorum wins the born-again vote in Arizona by nine points but loses among non-evangelical Republicans by 12 points. Romney loses by three points among tea party supporters but has a 15-point lead among Republicans who oppose the tea party or are neutral toward it."

The new poll indicates that Arizona's geography may also play a big role in the battle for the state's 29 delegates at stake in the primary, which are winner-take-all.

"Romney has a 10-point lead in urban areas, but manages no better than a tie in suburban and rural Arizona. As a result, Romney is ahead in Maricopa County but is tied, 33% to 33% in the rest of the state," adds Holland. Maricopa County is where Phoenix and its surrounding cities are located and represents roughly 60 percent of the state's population.

"Class and gender may also play a role on February 28, with Romney doing best among Republican women and among GOPers who describe themselves as white collar," Holland notes.

Michigan, the other state that votes on February 28, has 30 delegates up for grabs, which will be divided proportionally.

The CNN/Time poll was conducted by ORC International from February 17-20, with 467 registered Republicans who are likely to vote in the Arizona GOP presidential primary questioned by telephone. The survey's sampling error is plus or minus 4.5% points.