WASHINGTON • Mr Donald Trump's campaign has begun formally vetting possible running mates, with former House speaker Newt Gingrich emerging as the top candidate, followed by New Jersey Governor Chris Christie.
But there are more than half a dozen others being discussed as possibilities, according to several people with knowledge of the process. Given Mr Trump's unpredictability, campaign associates caution that the presumptive Republican nominee could still shake up his shortlist.
But with little more than two weeks before the start of the Republican National Convention, Mr Gingrich and Mr Christie have been asked to submit documents and are being cast as favourites for the post inside the campaign.
Mr Gingrich, in particular, is the beneficiary of a drumbeat of support from Trump confidants such as Mr Ben Carson.
A number of senators - including Mr Jeff Sessions of Alabama and Mr Bob Corker of Tennessee - are also being reviewed as viable picks, although the extent to which they are being vetted is unclear.
A longer shot on Mr Trump's radar is Indiana Governor Mike Pence, a heavyweight on the right who could bolster Mr Trump's tepid support among some conservative activists.
But Mr Pence is immersed in his re-election race and Mr Trump is said to want a more electric politician at his side rather than a low-profile figure.
Most of Mr Trump's rivals during the primaries are reluctant to sign on, and tensions with Ohio Governor John Kasich and Senator Ted Cruz of Texas remain raw.
Details of the running mate search were provided by five people with knowledge of the process who requested anonymity to discuss private conversations with campaign officials.
Mr Gingrich, who said on Fox News Sunday last weekend that "nobody has called me" from the Trump campaign about the possibility of being vice-president, declined to comment. Campaign spokesman Hope Hicks also declined to comment.
Mr Christie's office did not respond to an inquiry.
The narrowing list of possible running mates comes at the end of a turbulent period for Mr Trump, who has struggled to raise money since clinching the Republican nomination and has stumbled through a series of self-inflicted controversies, including a racially charged attack on a sitting federal judge and a continuing outcry over his rhetoric against Muslims and other minorities.
The presumptive Republican nominee continues to indicate that he will probably choose someone who could balance his brash populist persona with a political profile that includes deep experience in Washington or ties to the party establishment, said the people familiar with the search.
The timing of Mr Trump's announcement was for months expected to happen close to the convention. But campaign aides are now discussing moving it up, perhaps to later next week so that the ticket can generate headlines and coverage - and win over party leaders - ahead of the party gathering in Cleveland.
With Mr Gingrich, 73, or Mr Christie, 53, the 70-year-old mogul would be joined by a well-connected Republican who shares his combative style and his ease at being an ubiquitous media presence.
Both men have won Mr Trump's favour by actively supporting him - Mr Gingrich primarily through television appearances and Mr Christie through behind-the- scenes talks with party leaders and leading Republican donors.
Their experience facing down and cutting deals with Democrats has also drawn the interest of Mr Trump, who has acknowledged that he would be a novice at working directly with lawmakers.