AP

DES MOINES, Iowa (AP) -- Mitt Romney has released a new TV ad in Iowa -- one that portrays him as a conservative businessman who will shrink the federal government and stop the U.S. from spending more money than it takes in.

After a brief Christmas break, Republicans are returning to campaign mode with just a week to go before Iowa's leadoff caucuses.

The other candidates have fresh ads ready to air. After criticizing the negative tone of the campaign last week, Newt Gingrich is preparing to directly challenge Romney on the economy. He's expected to use clips from Romney's previous campaigns distancing himself from Ronald Reagan. And he's expected to compare Romney's tax plan with his own.

Romney is talking by phone today with supporters in Iowa, New Hampshire and Florida, and working on a speech that his aides describe as a final pitch to Iowans. After delivering that speech tomorrow evening, he's setting out on a bus tour of the state.

He'll be sharing the highways with Gingrich, Michele Bachmann and Rick Perry.

Each of them is looking to derail Ron Paul, the Texas congressman who seems to have the most sophisticated network of volunteers ready to organize ahead of the caucuses. He's kept in touch with supporters in the state since his unsuccessful run in 2008.