“If the money’s not coming in, you’ve just got to work harder and that’s what we’re doing. We’re going up in the morning doing radio shows at six in the morning and going until nine, ten at night and town meeting after town meeting. 357 in Iowa. Hard work pays off,” Santorum said.

Santorum, who has long said Iowa voters would come around to him eventually, said his message of social conservatism combined with strong national security was making a dent a week ahead of the first-in-the-nation caucus.

“We’ve always felt we could trust the people of Iowa, that when they got down to the time they were going to look at all the candidates and measure up to people they’ve had the opportunity to see, that they would do well,” Santorum said.

Mitt Romney, who led the Iowa poll at 25%, is too inconsistent in his message, Santorum said.

“His position on Romneycare, on marriage, on cap and trade, there’s a whole laundry list of issues where Mitt’s been all over the map,” Santorum said.

The former Pennsylvania senator said Romney’s record on gay marriage was particularly egregious, saying he should have done more to oppose Massachusetts’ state law.

“It’s clear he had a choice and he made the wrong choice,” Santorum said. “If you’re looking at someone who is a conviction politician, who’s not going to move around on the issues and present a clear contrast. Mitt Romney’s never proven to win in an election where he had to get independents as a conservative.”

Ron Paul’s history of opposing foreign military action by the United States presented another concern for Santorum.

“My concern is that Ron Paul would walk in there, day one, pull our troops back and leave an enormous void around the world,” Santorum said. “He can do that day one without congressional approval. He can, as commander in chief, move our troops anywhere in the world, disengage from every place from Europe to the Middle East, China, abandon the Strait of Hormuz, pull the 5th Fleet back. That’s one of the reasons I think you see folks who are having second thoughts.”

A British company has almost sold out two cruises for people to mark the anniversary on 15 April by following the route of the Titanic to where it struck an iceberg. The booming demand for Titanic-related travel has led to another travel company offering the chance to explore the wreckage of the ill-fated vessel in a Russian-built submarine next summer at a cost of $59,000 (£37,000) per person. Places for that voyage are already “very limited”.

The tourism boon is part of a general revival of the fascination with the Belfast-built steamship which will see special festivals take place on both sides of the Atlantic as well as the screening of a 3D version of James Cameron’s Oscar-winning film and a big-budget ITV drama by the Downton Abbey writer Julian Fellowes.

Such is the interest in places on the MS Balmoral, the vessel retracing the journey of the maiden voyage of the Titanic, that a waiting list for cancellations has closed.

Some of those who have booked berths costing up to £5,995 are having costumes made to recreate the appearance of the original passengers, while there have also been requests from musicians to audition for places on the string quartet that played as the flagship of the White Star Line fleet began to list.

Miles Morgan, managing director of Titanic Memorial Cruises, the Bristol-based company organising the events, said places on the cruise from Southampton had sold out weeks after going on sale, with the second cruise likely to sell out by next month and interest in the commemorative journey remaining intense. He said: “We have been approached by news crews all over the world who want to film our recreation of the fateful voyage. We could probably have filled the entire vessel just with journalists wanting to be there. The interest has come from all over the globe – we’ve had people from 24 different countries booking.

“I think that is testimony to the fact that the name of the Titanic has become one of those words that is recognised in any language around the globe. There are so many stories associated with the ship, from its own tragic history to the stories of those that lost their lives, that people remain deeply fascinated by it.”

The culmination of restaging the Titanic’s voyage – which will see the Balmoral, a chartered vessel belonging to the cruise line Fred Olsen, sail to the point off Newfoundland, Canada, where the ship collided with an iceberg – will be a memorial service at 2.20am on 15 April – the moment when what was then the world’s largest passenger ship sank.

A second vessel chartered by the cruise company to carry 694 people will also meet at the site of the sinking after sailing from New York en route to Southampton. And plans are being made for the wireless radio station at Cape Race in Newfoundland, which received the Titanic’s SOS in morse code, to repeat the message.

Among those on board the Balmoral will be relatives of victims and survivors of the Titanic, including Philip Littlejohn, the grandson of Alexander Littlejohn, who was a steward in the first-class section of the vessel and survived by rowing away one of the 16 lifeboats on board. The small number of lifeboats meant that barely a third of the ship’s complement of passengers and crew could ever have been saved.

The attention to detail for the recreated Titanic voyage means that passengers will dine on the same menus offered to the 1,514 people who died and the 710 who survived when the ship struck an iceberg at 11.40pm. Among the items from the 11-course first-class dinner to be offered will be oysters, roast squab and sautéed chicken Lyonnaise.

Mr Morgan, who pointed out that the engineering and safety rules of modern ships mean that icebergs now pose no danger to the cruise, said it was wrong to criticise the commemoration as “voyeuristic”. He said: “I take my lead from those people who are coming on board who lost relatives in the disaster or whose family members survived. They have all said that they could not think of any better way to mark the memory of those who were lost than being at the site of the sinking to pay their respects.”

The voyages: Then & now

RMS Titanic

Day 1: Departs Southampton.

Day 3: Sails through calm waters.

Day 4: Passengers in first class enjoy 13 courses including oysters, roast duckling, foie gras.

Day 5: Seven iceberg warnings. Hits iceberg at 11.40pm.

Day 6: Sinks at 2.20am.

Memorial cruise

Day 1: Departs Southampton.

Days 3 and 4: Gym, spa, history talks.

Day 5: No collisions scheduled.

Day 6: Memorial service at 2.20am.

Day 7: Arrive at Halifax, Canada, and visit Fairview Lawn Cemetery, where victims are interred.

Day 8: Arrive in New York – the Titanic’s intended destination.