TUCSON, Ariz. -- The next 24 hours could be the most decisive of former Pennsylvania senator Rick Santorum’s political career.

Republican presidential candidate, former Pennsylvania senator Rick Santorum speaks during a campaign rally at the El-Zaribah Shrine Auditorium, Tuesday, Feb. 21, 2012, in Phoenix, Arizona. (AP Photo/Eric Gay)

If Santorum’s remarks at a Phoenix town hall Tuesday night are any indication, he plans to give a strong defense of some of his more controversial campaign-trail comments, trying to use the controversy that has flared in recent days to his own advantage and casting himself as a more authentic candidate than former Massachusetts governor Mitt Romney.

Santorum will likely be asked about his comment that President Obama believes in a theology not based on the Bible; his opposition to prenatal screening; and a recently-resurfaced 2008 speech in which he repeatedly referred to Satan and described a “spiritual war.”

That gives him an opportunity to focus the debate on himself, rather than on his opponents, and to argue that he’s the candidate who could best draw a contrast with Obama in the fall.

It could be a pivotal moment for Santorum, who is rising in the polls and now has nearly pulled even with Romney in Arizona and now leads in several other key states.

How will Romney respond if Santorum repeats his suggestion that Romney is “robotic” and consultant-driven? Will Santorum take on Romney directly, or will he stick to his stump-speech message that he’s waging a “positive” campaign? (A national debate is quite a different venue from a campaign rally, so that theme of positivity may not necessarily play as well as it has for Santorum on the stump.)

On top of the high-stakes build-up, it’s also Ash Wednesday, meaning that the faith of the two Catholics in the race – Santorum and former House speaker Newt Gingrich – may be literally on display.

Ahead of the debate, Rep. Ron Paul (R-Texas) holds two fundraisers in Mesa, while Santorum and Romney hold rallies. Gingrich visits an elementary school in the afternoon.

Here’s a closer look at today on the trail (Courtesy of candidate schedules and the PBS NewsHour Political Calendar; all times Eastern):

11 a.m.: Ron Paul holds a fundraiser in Mesa, Ariz.

11:50 a.m.: Mitt Romney holds a rally in Chandler, Ariz.

1:50 p.m.: Rick Santorum addresses a tea party rally in Tucson, Ariz.

2 p.m.: Ron Paul holds a fundraiser in Mesa, Ariz.

3 p.m.: Newt Gingrich visits an elementary school in Gilbert, Ariz.

8 p.m.: CNN holds a GOP presidential debate in Mesa, Ariz.

10:30 p.m.: Newt Gingrich stops by a debate watching party in Scottsdale, Ariz.