FILE PHOTO: U.S. Vice President Mike Pence attends a news conference at the U.S. Embassy in Ankara, Turkey, October 17, 2019. REUTERS/Huseyin Aldemir

WASHINGTON (Reuters) - Vice President Mike Pence will begin a push on Wednesday to bolster President Donald Trump’s position in Wisconsin, Michigan and Pennsylvania, three states that Trump won narrowly in 2016 and probably must win again to secure a second term in 2020.

Pence will travel to northeastern Wisconsin on Wednesday to visit shipbuilder Marinette Marine to talk up the trade agreement between the United States, Mexico and Canada that Trump negotiated, but which has yet to receive congressional approval.

But the overarching mission, people close to Pence say, is to wave the Trump campaign flag in Wisconsin, a state Trump won by only 23,000 votes in 2016.

In early December, Pence will make stops in Michigan and Pennsylvania, two other states Trump won narrowly over Democrat Hillary Clinton in 2016. These visits will include bus tours, a departure from Trump’s traditional campaign style of staging rallies in large arenas.

The Pence visits come as Trump is preoccupied in Washington with an impeachment inquiry in the Democratic-controlled House of Representatives that is dogging his presidency.

Trump has lagged in recent polls in the three industrial states when compared to his leading Democratic rivals, leading some Republican strategists to wonder why Trump and his campaign were not spending more time in them if he wants to recreate the electoral map that carried him to victory in 2016.

“The three states were key to his 2016 victory and he needs two win at least two of them and keep everything else in order to win re-election,” said one Republican strategist close to the campaign. “These are battleground states and you need to show up regularly and effectively.”

In recent weeks the Trump campaign, riding a surge of money from donors, has sought to expand the electoral map into some states Trump lost in 2016, such as Minnesota, New Mexico and Oregon.