WASHINGTON - With their presidential nomination all but settled, Republicans are now turning to the question that will dominate their spring: Who will be Arizona Sen. John McCain's running mate?

Party activists are more interested than usual in his pick for three reasons:

* He needs to shore up support from conservatives, and the running mate is his best chance to do that;

* The vice presidential nominee could be first in line to win the presidential nomination the next time it's open;

* Given McCain's age -- he'd be 72 on Inauguration Day -- the presidency could come open sooner than eight years .

The most-discussed name right now is former Arkansas Gov. Mike Huckabee, who is staying in the campaign despite the fact that he almost certainly cannot wrest the nomination away from McCain.

McCain campaign manager Rick Davis last week seemed to dismiss the prospect when asked whether Huckabee would bolster the ticket's chances at attracting change-minded voters.

"I'm not sure how much help John McCain needs being a change agent," Davis said. "That being said, I think we have other options to look at vis-a-vis the ticket."

McCain doesn't have to announce his pick for months -- certainly not until he knows who the Democrats will nominate as his opponent, and perhaps not even until just before the Republican National Convention starts in St. Paul on Sept. 1.

But as he draws up his own list, here's a set of names, with the pros and cons of each person most often mentioned by Republicans:

HALEY BARBOUR, 60, governor of Mississippi

Pro: Popular former national party chairman helped Republicans win Congress in 1994 and got very good reviews for his leadership when Hurricane Katrina struck his state in 2005.

Con: A long record as a Washington lobbyist that could clash with McCain's reform message.

CHARLIE CRIST, 51, governor of Florida

Pro: He's a popular governor whose endorsement helped McCain win the critical Florida primary. As running mate, he'd probably help put this big swing state solidly in the Republican column.

Con: His refusal to back an anti-gay marriage initiative and appointment of Democrats to head state agencies tar him as suspect to the party base.

MIKE HUCKABEE, 52, former governor of Arkansas

Pro: He's shown his ability to win in the South and has support among evangelical Christians. A solid social conservative.

Con: He raised taxes as governor and supported equal benefits for the Arkansas children of illegal immigrants. Picking him might not excite conservatives.

KAY BAILEY HUTCHISON, 64, senator from Texas

Pro: Offers a gender balance to the ticket and wins handily in her mega-state.

Con: Support for financing embryonic stem-cell research worries social conservatives. Also, she's probably more interested in running for governor.

CONDOLEEZZA RICE, 53, secretary of state

Pro: First black woman on the ticket provides racial and gender balance against a Democratic ticket sure to have either a black or a woman.

Con: Nobody knows what she thinks about hot-button issues from abortion to taxes. Also, her record on Iraq and other security issues could provide a running debate with her own running mate, who criticized many of those stands.

MARK SANFORD, 47, governor of South Carolina

Pro: Young, vibrant conservative with a record of fighting spending while in the House, a McCain theme.

Con: Wouldn't add a state to the McCain column. McCain should carry South Carolina without him.

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