Retailers keep trying to inspire Americans to start their holiday shopping early.

With 102 Christmas seasons under its belt, J.C. Penney Co. is among retailers that have decided it’s not very effective to blitz consumers with holiday ads too early.

The Plano, Texas-based company is throwing its muscle behind messages that begin in earnest Wednesday, said Mike Boylson, executive vice president and chief marketing officer.

“The big-money spending begins Thanksgiving week,” he said. “Some retailers started pushing Christmas before Halloween, but I think if you’re not careful, the customer will rebel against that.”

After last year’s disappointing Thanksgiving weekend, Wal-Mart Stores Inc. moved up its holiday advertising campaign to Nov. 1, its earliest-ever launch. Whether it’s working is still under assessment, said spokeswoman Gail Laville.

RadioShack Corp. started its campaign about the same time as last year – in the first week of November. But it saved a big, new marketing idea for the weeks between Thanksgiving and Christmas, spokesman Charles Hodges said.

The fact is, the closer it gets to Christmas, the more American shoppers say they intend to spend on holiday shopping, according to Frank Newport, Gallup Poll editor-in-chief.

“Estimates obtained in December are higher than those measured in November,” he said.

Shoppers always say they’ll be frugal early in the season but tend to open their wallets once they’re in the Christmas spirit, he said. Last year, spending estimates rose from $730 in mid-November to $862 in mid-December, according to the poll. And seasonal sales beat estimates, rising 6.7 percent.

Newport also considers year-over-year spending averages key. The latest poll, conducted Nov. 7-10, found that shoppers expect to spend an average of $763 on gifts this season. That estimate is up from $730 the same week last year and is the highest since November 2000, he said.

The National Retail Federation raised its forecast for the season on Monday, saying sales would rise by 6 percent instead of the 5 percent it had forecast earlier.

Penney’s Boylson labeled this season a “nail-biter” – not so much for its outcome, but for when people will shop.

“It will come late and hard,” he said. “We’re prepared for a violent peak at the end.”

Wal-Mart said its comparative sales remained on track to increase 3 to 5 percent this month. However, going into the biggest week of the month, Wal-Mart said food sales trends were stronger than general merchandise.

“We’re a bit early still in the holiday season. Now the customer has had a good look at what we have to offer. We’ll have a better assessment later,” said Wal-Mart spokeswoman Laville.

Wal-Mart’s ads aren’t necessarily targeted to new shoppers because Wal-Mart doesn’t lack customers, she said.

“We’re trying to get people already in our stores to shop the rest of the store,” Laville said. “If we could do that, then we’re fine.”

Wal-Mart has beefed up three large holiday categories – apparel, electronics and furniture/home – with new merchandise and price points leading up to the season.

“I think this is the trickiest holiday season for retailers that we’ve seen in a decade,” said Marshal Cohen, chief retail industry analyst at the NPD Group. “There really are no hot items. What the retailer is selling is popular items – and they’re everywhere. So the competition is everybody.”

And that puts the consumer in the driver’s seat, he said.

“Retailers will be pulling out the promotions, and each one will be trying to keep you in their store the longest,” Cohen said.

RadioShack is bringing a high-tech red chair from its commercials to malls across the nation this week. It takes direct marketing to a new level.

“Real people will sit in the chair and we’ll record them talking about their gift wish and e-mail it for them,” said spokesman Hodges.

While consumers are waiting until they’re good and ready to start their holiday shopping, they don’t mind extending the season.

As more gift givers choose gift cards, Christmas shopping has stretched into the week after Christmas, Cohen said.

“Smart retailers need to have something fresh for that customer,” he said. “Some stores are going to flow in new merchandise in late December and early January because they need to have their best foot forward for the gift card shopper.”