Washington - In picking a vice-presidential running mate, Republican Mitt Romney wants to avoid the Sarah Palin syndrome.
Then-Republican nominee John McCain shook up the 2008 race with his dramatic choice of the relatively unknown Palin, but the problems she faced during the campaign will be on the minds of Romney and his vice presidential search team.
The presumptive 2012 nominee, Romney is expected to make a steady, "do-no-harm" choice and avoid the type of "Hail Mary" selection that Palin represented, in his bid to unseat President Barack Obama.
Aides say Romney wants someone with deep, rock-solid experience who could take over the presidency if needed. Being able to work well as a team player is also essential.
Romney seems unlikely to pick a No 2 from the group of candidates who ran for the nomination this year and lost.
That would rule out Newt Gingrich, Rick Perry, Michele Bachmann, Jon Huntsman, Ron Paul and Herman Cain. It seems doubtful that Romney's last chief rival, conservative Rick Santorum, would be selected although he may end up on the short list for appearance's sake.
Plucked out of obscurity
But Tim Pawlenty, a conservative former Minnesota governor, is popular within the Romney campaign and will likely be given consideration. Well-regarded by evangelicals, Pawlenty has spoken up for Romney since he pulled out of the race.
Most Republicans want a candidate who at the very least will not damage Romney's chances of defeating Obama and, ideally, would bolster the ticket.
Palin, the former Alaska governor, energised the Republicans' conservative base and still does.
But in the 2008 campaign, her lack of knowledge about global affairs and her inability to name a newspaper she reads, made her the stuff of late-night comics and ultimately undermined McCain's candidacy.
This would seem to limit the chance that someone could be plucked out of obscurity, as Palin was.
"There's surprise and then there's big surprise, and I think you want a lower-case surprise," said Republican strategist Tucker Eskew.
Decision in late August
One other factor Romney must weigh is whether to make a glitzy choice who could excite Republicans but overshadow Romney himself, like New Jersey Governor Chris Christie.
"Clearly there are risks to having someone who is more dynamic or who is more of a firecracker than yourself," said Republican strategist Ron Bonjean. "The benefit of having a someone who is much more dynamic than you is that it creates excitement around your candidacy. The downside is if this person goes off message and over-reaches, it can have a negative impact on the campaign."
A decision is unlikely until just before Republicans meet in Tampa in late August to crown Romney as their nominee.
Here's a look at who many Republicans think are the top contenders, the second-tier candidates and the long shots.
The focus of the greatest speculation has been on five big names in the party: Three are Ohio Senator Rob Portman, Florida Senator Marco Rubio and Wisconsin Congressman Paul Ryan, chairperson of the House of Representatives Budget Committee.
Rounding out the top five are New Jersey's Christie and Louisiana Governor Bobby Jindal.
- Portman, aged 56, endorsed Romney early on and campaigned with him in Ohio, helping the former Massachusetts governor to a narrow win in a battleground state that will be key to whether Romney wins the White House.
Portman is a relatively low-key but deeply experienced politician and would be seen as a safe, steady choice.
But as a former budget director for Republican President George W Bush, Portman would be an easy target for Democrats, who could accuse him of contributing to the dire fiscal shape the government's finances are in.
He also served as US trade representative, which could be crucial experience in Romney's desire for expanding US exports abroad and fairer global trade. He has not ruled out accepting a vice presidential nod.
- Rubio, aged 40, is a Cuban-American who, if selected, would be seen as a bridge to the growing Hispanic population that votes heavily in favour of Democrats. All eyes will be on him on Monday as he campaigns in Pennsylvania with Romney.
Republicans acknowledge the need for attracting a greater percentage of Latinos to their party. At the same time, picking him could energise conservatives who have been less than enthusiastic about the more moderate Romney.
Counting against Rubio would be his relative youth and inexperience. He has only been a senator since his 2010 election and has no major legislative track record.
Many Republicans see him as a contender for the 2016 Republican presidential nomination itself, which could be a big reason why he might want to sit out 2012.
Rubio on Sunday touted former Florida governor Jeb Bush as a "fantastic" choice as Romney's running mate but remained coy about whether he himself would accept such an offer.
- Ryan, aged 42, bonded with Romney during the Wisconsin primary in April as the two criss-crossed the state together. He is a rising star within the party.
"He is always a very strong leader of the Republican Party," Romney told Fox Radio of Ryan. And picking him could help Romney win Wisconsin, a state that has eluded Republicans in recent elections despite vigorous campaigns there.
What Romney and his aides will have to debate is whether picking Ryan would make his controversial budget-cutting plan a central feature of the campaign.
Ryan's 2013 budget blueprint would cut $5 trillion more than Obama has proposed and would make deep cuts to Medicare and Medicaid social programmes for the poor and elderly. Romney has given general support to Ryan's plan but not an outright endorsement.
Whether Ryan has sufficient life experience outside of Washington could also work against him. By choosing Ryan, Romney would be making a statement that it is fine to make the race a referendum on the US budget and the Ryan plan.
Ryan has said he would consider being the No 2. "If this bridge ever comes that I should cross it, then I'll think about it then. It's not the time to think about it," he told the Wall Street Journal.
- Christie, aged 49, is a rock star in the Republican Party. He chose not to run for president in 2012 and instead endorsed Romney. He has been an effective advocate for him on the campaign trail.
As a Republican governor in a mostly Democratic state, he has taken on entrenched Democratic institutions there with fervour. A bombastic politician who is fluent on the issues, Christie would be an ideal attack dog on the campaign trail.
Some conservatives would frown on the pick, fearing he is too moderate. Some Republicans also worry that the contentious Christie could be a distraction with his verbal fire-bombs, or overshadow Romney, who sometimes has trouble connecting with voters.
Also potential concerns are Christie's massive girth and whether his health could withstand the pressures of the job.
A Quinnipiac University poll last week found him the lead choice of likely voters for the No 2 slot. He hasn't ruled it out.
"If Governor Romney comes to me and wants to talk about it, I'll always listen," he told a town hall event earlier this month.
A timid pick
- Jindal, aged 40, is a major voice in the conservative movement and could help Romney patch up relations with a base that was reluctant to choose him during the long, bitter primary fight. Jindal is an Indian-American and former member of the US House of Representatives.
As governor, he grappled with the fallout and recovery from the 2010 BP oil spill that shattered fishing communities along Louisiana's Gulf coast, and was seen as handling it well.
When given a big opportunity on the national stage, however, he flubbed when he delivered the Republican response to Obama's 2009 speech to a joint session of Congress.
The question for Romney would be whether Jindal is too timid a pick for the attack-dog role the vice presidential candidate often plays. He has not ruled out accepting the VP nod if asked.
Beyond those five, the secondary possibilities include Pawlenty, Virginia Governor Bob McDonnell, former Florida Governor Jeb Bush and Indiana Governor Mitch Daniels.
- Pawlenty would bring a reliably conservative voice to Romney's team and would appeal to evangelicals, whose energy and enthusiasm will be needed to turn out the vote. His problem during his failed 2012 campaign was that he was not an electrifying presence on the trail.
- McDonnell backed Romney early on and could help deliver his home state to the Republicans after they lost it to Obama in 2008. Then again, the growing population of Democrats in Northern Virginia could mean Obama wins it again even with McDonnell on the ticket.
McDonnell would face questions about a law he pushed through the state legislature requiring women to have an ultrasound procedure before having an abortion.
Romney opposes abortion but may want to avoid anything that could distract from his central economic message. Republicans are having enough trouble appealing to women voters as it is, which is why McDonnell is unlikely to be the choice.
- Jeb Bush would be a bold choice because he could overshadow Romney. A conservative, Bush has led the national debate on reforming the US education system, and he could help Romney win the crucial battleground state of Florida.
He is often mentioned as a future presidential candidate. His biggest problem is simply sharing the Bush name, after his brother, George W Bush, left the White House in 2009 as an unpopular figure.
While Republicans in general would have no problem with a Bush on the ticket, independent voters who will be key to the election could be turned off. Chances are that Bush sits out 2012 and contemplates a 2016 race for the presidency.
In the mix
- Daniels drew rave reviews for a speech in 2011 that declared America's debt crisis a new "red menace". He opted against a presidential run despite ardent pleas for him to make a late leap into the campaign.
Daniels cited family reasons for deciding not to run. His personal story is complicated. He was divorced after his wife left him with their children for another man, but they were later reunited in what Daniels called a classic love story.
He may want his family to avoid media attention. He has said he does not want to be considered by Romney.
Toss into the mix these names as well:
- New Hampshire Senator Kelly Ayotte has close ties to Romney and campaigned heavily with him in her home state in the Republican primary. She might be too inexperienced, since she has only been in the Senate for less than two years.
- A pair of Hispanic governors, Nevada's Brian Sandoval and New Mexico's Susana Martinez. Choosing one or the other would signal Romney's intention to compete strongly for the Hispanic vote, which could be pivotal in Southwestern states.
Martinez is relatively inexperienced, only serving as governor for 15 months, and may be likened to Palin as a little-known woman governor from a small state. Martinez has said repeatedly she is not interested in serving as vice-president.
- Former US Secretary of State Condoleezza Rice would provide deep foreign policy knowledge. She has said repeatedly she does not want to be considered. But Republicans in a poll last week cited her as their top choice for the job.
Her downsides are that she has no real record on domestic policy issues and her tenure as a top Bush aide linked to the unpopular wars in Iraq and Afghanistan.
She has also shown little inclination to leave academic life at Stanford University. But the lure of being the first African-American woman to become vice president could be hard to pass up.