As the Republican presidential race spirals into a heated battle between Mitt Romney and Newt Gingrich, viewers of Tuesday’s State of the Union address will be reminded of what could have been.

Namely, Mitch Daniels.

Indiana Gov. Mitch Daniels (R) speaks during a news conference on the signing of a landmark education bill in April. (AP Photo/AJ Mast)

Since Daniels was announced as the responder last week, conservative columnist Bill Kristol fantasized about Daniels using his response to launch a campaign, an online petition urging Daniels to run for president (again) was posted, and former White House chief of staff and Chicago Mayor Rahm Emanuel (D) even suggested Daniels would have been the “perfect contrast” to Obama.

In fact, many of things that made the GOP establishment pine for Daniels in the first place have made him a valuable figure to trot out at this particular point in the GOP race.

To wit:

* Daniels is and always has been the adult in the room. While he is definitely a conservative and hasn’t been afraid to show it, he’s also been pragmatic.

One of the big knocks on him when he was considering a presidential run was that he had called for a “truce” on social issues. Also, until recently, he declined to embrace a bill that would make Indiana a “right to work” state – i.e. reining in the influence of unions.

And while those two things might not have helped him in the GOP presidential campaign, they have earned Daniels a reputation as a strategic governor who picks his spots and focuses on what’s important and doable.

Daniels, in that way, could serve as a good example for presidential campaigns that seem headed for the lowest common denominator.

* While other GOP governors have struggled with perceptions of their budget-cutting measures and battles with unions, Daniels is perhaps the one who has come out clearly on top in that regard.

According to Indiana political analyst Brian Howey, a December poll from GOP pollster Public Opinion Strategies showed Daniels with a 65 percent approval rating – a nearly unthinkable number for most governors in tough economic times, and especially one who is entering his eighth year in office (after all, that’s A LOT of time to get on peoples’ bad sides).

More than perhaps any other Republican governor, Daniels is the one who could have run on his record and contrasted it with that of President Obama, which is a big reason some wish he would have run.

“Mitch is one of the best governors in the country,” said former Florida governor and Daniels ally Jeb Bush (R). “There is definitely a place for him on the national stage.”

* Daniels is smart. This was seen as perhaps his biggest selling point and the thing that was supposed to help him overcome whatever stylistic problems a Daniels candidacy might have had.

In an economically focused election in which Romney is fond of pointing to his private sector experience and Gingrich has pointed to the balanced budgets during his speakership, both men are finding those experiences to be double-edged swords. Daniels wouldn’t have been the perfect GOP primary candidate in that regard — he has said he is open to tax increases in the past — but he is a former director of the Office of Management and Budget who could probably talk about the economy at a level nobody in the GOP race has, to this point.

And this is really the reason that some say his candidacy was their ticket to beating Obama.

We should get a taste of that in Tuesday night’s response. The question is whether it will leave Republicans, who are still trying to sort things out, pining for the candidate who could have been.

“Had he got in, I think he would be in the mix,” said one admirer. “He has the business experience and ... the organization that people like in Romney, without the baggage of Gingrich. He also makes a better foil for Obama than perhaps any of the candidates in now.”

At least for one night, Daniels will be that foil. And given that many see him as an attractive potential vice presidential candidate, it may be a sign of things to come.