(CNN) — As the clock ticks toward the start of the primary and caucus calendar, campaigning here in the Hawkeye state kicks into high gear.

Five of the major Republican presidential candidates will campaign in Iowa on Tuesday with one week to go until the state’s January 3 caucuses, the first contest in the race for the GOP nomination. And as the candidates criss-cross the state, Iowa airwaves will see an explosion of campaign TV commercials, following a brief lull for Christmas.

Texas Gov. Rick Perry, former Sen. Rick Santorum of Pennsylvania and Rep. Michele Bachmann of neighboring Minnesota on Tuesday resume barnstorming across Iowa, concentrating most of their firepower in the Hawkeye State in hopes of top-tier finishes.

Former House Speaker Newt Gingrich is back in the state for the first time in nearly a week, returning as he has lost his frontrunner status in the latest polls of likely Iowa GOP caucus-goers.

The latest survey, from American Research Group, finds a three-way traffic jam for the top spot, with Rep. Ron Paul of Texas at 21%, former Massachusetts Gov. Mitt Romney at 20% and Gingrich at 19%. Paul doesn’t resume campaigning until Wednesday, with Romney ending Tuesday in Davenport, Iowa, after starting the day with campaign events in New Hampshire, which votes second in the calendar, a week after Iowa.

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