Donald J. Trump will expand his roster of pollsters, with plans to add three new ones as his team shifts gears toward a general election with new urgency, according to a person briefed on the matter.

Mr. Trump, who once decried the use of pollsters on a campaign, will now have five polling firms working for him, according to the person briefed on the hires, who was not authorized to speak publicly.

Kellyanne Conway, a veteran pollster who has had a long working relationship with Mr. Trump, is among those joining the effort. Ms. Conway was the president of the leading “super PAC” supporting Senator Ted Cruz in the Republican nominating contests. She also did preliminary work for Mr. Trump when he considered a presidential campaign in 2011, and is expected to have a senior strategic role in this one.

Mr. Trump’s team is also expected to bring on Adam Geller, who works with Gov. Chris Christie of New Jersey, and Michael Baselice, who was the pollster for former Gov. Rick Perry of Texas and for the state’s governor now, Greg Abbott.