Threatened despite a slight advantage in polls, Romney went on the air with ads in the final days that take McCain to task on taxes and immigration. McCain claims the criticism proves his rival's bid is in trouble. He responded with his own commercial that quotes newspaper editorials praising him and eviscerating Romney, including one that suggests his rival is a "phony."

Huckabee has gained ground here since early this year but he still dramatically lags his rivals. His New Hampshire organization is thin, but he could be a force here if he leaves Iowa a winner.

Giuliani, a Northeasterner, tried to play here, but his $3 million TV ad campaign failed to boost his standing. As McCain surged, Giuliani dipped. He since has re-focused on his original strategy of winning delegate-rich states that vote later, beginning with Florida.

Paul could have an impact in the "Live Free or Die" state.

Independents who can vote in either primary and helped McCain in 2000 are the X-factor; there's no guarantee they will vote in the Republican matchup over the star-studded Democratic race.

New Hampshire has 24 pledged delegates, but Republican Party penalties will cut the number to 12.

Michigan: Jan. 15

Giuliani's once-strong support has plummeted. That's left a tight contest between Huckabee, whose success elsewhere has reverberated here, and Romney, who grew up in the state where his father was a governor. McCain won the state in 2000 and has some support here.

None of the candidates has given Michigan the attention it sought when it moved its primary to an early date. National party sanctions have cut the number of Michigan delegates from 57 to 30.

The results from Iowa and New Hampshire could upend the race.

Nevada: Jan. 19

This Western state and its 34 delegates are a wild card. Republicans have hardly campaigned in a state that's geographically inconvenient. Nevada also holds caucuses that demand a stellar organization and boatloads of money. Most candidates don't have both. Polling shows Romney, Huckabee and Giuliani competitive.

South Carolina: Jan. 19

Huckabee has an edge in this first-in-the-South primary battleground with the support of fellow white Christian evangelicals. But his lead is narrow. Romney and McCain are competing hard.

Although he lags both in organization and money, Huckabee could benefit from religious leaders rallying their followers.

Romney has maintained his popularity despite Bible Belt uneasiness about his religion. McCain, who lost a nasty primary here in 2000, wants South Carolina to be the second stop on his comeback tour.

Giuliani's rocky personal life and left-leaning positions on abortion and gay rights may be catching up with him in this conservative hotbed. South Carolina would seem a natural fit for Thompson the Tennessean, but money woes have limited his efforts here.