Newt Gingrich said Friday that "you have to look at it very seriously, of course" regarding the possibility of being presumptive Republican nominee Donald Trump's running mate."I regard Donald as an old friend," Gingrich, the former Georgia representative who was House speaker from 1995 to 1999, toldon Fox News.Gingrich, 72, said that he his wife, Callista, "have regularly talked with him for the last five or six years during the campaign occasionally. I do more of it by email than I do phone."We have communicated on a routine basis with the campaign and with Trump and his family."Tuesday that Gingrich topped Trump's list of possible vice presidential choices. The developer said that he was seeking a partner while deep experience within Washington who could help him ""with legislation, getting things through.""There are a lot of very good candidates who know a great deal," Gingrich told O'Reilly."He has been very clear that he wants an insider because he understands that while he has done an amazing job arousing the country, building a real movement, to get things done in Washington — as he proved in the visit yesterday — you have got to sit down and talk to the legislators."I don't know who is on the list."In a separate interview Friday, Gingrich said that casino mogul Sheldon Adelson's endorsement of Trump would go a long way toward helping him raise money."It’s a very big signal," he toldAdelson, the billionaire CEO of the Las Vegas Sands casino group and head of the Republican Jewish Coalition,in The Washington Post that he was endorsing the developer because "the alternative to Trump being sworn in as the nation's 45th president is frightening."In the 2012 primary race, Adelson backed a Gingrich super PAC against Mitt Romney."Everyone knows that Sheldon is a very serious man — and to have Sheldon come in as strong as he did" will bring aboard other Republicans, Gingrich said.