ABC's Amy Walter and Shushannah Walshe report:

In a sign of Rick Santorum's mounting confidence over a strong showing in Iowa, a senior strategist with the campaign tells ABC News that the campaign is going up with ads on South Carolina TV starting next Wednesday.

The South Carolina primary takes place January 21. He's made over 25 visits to South Carolina state so far.

The South Carolina electorate, with its heavy population of evangelical voters, is more hospitable territory for the socially conservative Santorum than New Hampshire, which has a more moderate leaning electorate.

Furthermore, Romney has a substantial lead in the Granite State while the South Carolina primary is wide open.

The size of the buy is not known, but it does suggest that Santorum has raised enough cash to take the gamble on ads for a primary that is still three weeks away.

Santorum won't be just skipping over the Granite State though. He will be in the state the day after the caucuses, which will be his 30th to the first primary state. He's also going up on the air there Monday.

A new television ad titled "Best Chance" is going on the air today in Iowa and next week in New Hampshire. This is the first time the campaign will be on the air in the Granite State.

"Who has the best chance to beat Obama? Rick Santorum," the voice over says over a photo of President Obama and video of Santorum with his family and on the stump. "A full spectrum conservative, Rick Santorum is rock solid on values issues."

The ad also touts his "tea party ties," "foreign policy credentials" and economic plan.

The buy is also not known, but like the South Carolina ad buy it shows less of a shoestring budget they have previously been working with and an aggressive push to be the anti-Romney in the race when every other GOP candidate has failed to do so.

A new television ad titled "Best Chance" is going on the air today in Iowa and next week in New Hampshire. This is the first time the campaign will be on the air in the Granite State.