Washington - Republican Donald Trump has narrowed down his vice presidential shortlist to a handful of contenders. While the presumptive GOP nominee is known for throwing curve balls, here's a look at some of the men and women he is said to be considering and has met with recently:Newt GinrichTrump has long said that he's looking for an experienced insider who knows the ropes of Congress to pass his agenda. If that's what he wants, there's arguably no one more qualified than the former House speaker who represented Georgia in Congress for 20 years.Gingrich, who ran his own bid for president four years ago, has become a trusted informal Trump adviser, and brings a wealth of policy ideas to the table along with deep connections.But he's also made clear that he's not afraid of criticising Trump publicly when he thinks he's wrong - something Trump does not typically embrace.Some Trump allies also worry that Gingrich's presence on the ticket would turn the race into a re-enactment of his 90s-era battles with the Clintons. And it's unclear how eager Trump is to share the spotlight with another forceful personality.Not to mention the pair have been married six times combined.Chris Christie In the months since his surprise endorsement, the New Jersey governor has become one of Trump's closest confidantes, offering advice during crises and appearing by Trump's side at public events and fundraisers. Christie is also one of his party's most effective attack dogs and a talented retail campaigner, and has proven a crowd-pleaser on the trail.The two have also been friends more than a decade, giving Christie the upper-hand if Trump decides to go with the candidate he feels he knows best.But a Christie selection would also come with considerable baggage.After several months of largely fading from the headlines, the controversy over the George Washington Bridge scandal has recently re-emerged with questions over what happened to the cellphone Christie used during the aftermath of the controversy and the potential release of a list of unindicted co-conspirators in the case.The criminal trial involving former Christie aides is currently scheduled to begin in September — at what would be the height of the presidential contest.Christie's poll numbers have also hit rock-bottom at home in New Jersey, and the state's economic woes could become an issue on the trail.Mike PenceTrump met with Pence and his family over the weekend and apparently Pence left a good impression.Trump tweeted on Monday that he was "very impressed" by the Indiana governor, who at one time had his own presidential ambitions. In addition to his time as governor, Pence served in the US House of Representatives for 12 years.Trump, who values loyalty, doesn't know Pence as well as some of the other candidates under consideration.But Pence, who was once a favourite of social conservatives, has also seen his standing slide in the wake of criticism over his handling of the state's "religious freedom" law, which critics feared would allow discrimination against gays and lesbians. After repeatedly defending it, Pence eventually signed a new version of the bill with additional protections that left both sides dissatisfied.Jeff SessionsThe first senator to endorse Trump's presidential bid, Sessions has become a top cheerleader and close Trump confidante, especially when it comes to shaping his policy positions. The two share similar approaches on a host of issues, including hard-line views on halting illegal immigration.Sessions is not as well-known as some of Trump's other choices, and it's unclear whether his mild-mannered persona would deliver the kind of splashy punch Trump is hoping to achieve with the announcement of his running mate.But Sessions, who previously served as US Attorney in Alabama, has proven a loyal resource and ally - something that Trump especially favours.Joni ErnstErnst shot to national fame in 2014 with a TV ad in which she boasted about castrating pigs and promising to cut the pork in Washington and "make 'em squeal."A former state lawmaker and military veteran with a rural upbringing, Ernst has been considered a rising star in the Republican Party since she became Iowa's first woman in Congress in 2014.In addition to adding military experience to the ticket, Ernst's inclusion might also help Trump improve his appeal among women voters, with whom he currently lags.But Ernst also has just two years of federal government experience and many top Iowa observers say they would be surprised to see her picked.The pair met on Monday and had "a good conversation" about issues concerning Iowans, she said in a statement. But Ernst did not say whether the vice presidency was discussed.Bob CorkerCurrently the chairman of the Senate Foreign Relations Committee, Corker would bring serious foreign policy chops to a Trump ticket.Corker was one of the highest-profile Republicans to praise a major foreign policy speech Trump delivered this spring. But he has also not shied away from criticizing the billionaire businessman, including over Trump's attacks against an Hispanic judge.The pair met at Trump Tower in New York in May to get better acquainted, sparking VP speculation, though Corker has so far remained mum about whether he is being vetted for the job.