President Trump's net approval rating has plunged in every key battleground state since taking office in January 2017, according to Morning Consult's tracking poll.

Why it matters: These are the states that Republicans and Democrats are vying for in 2020 and where, as of now, the campaigns think the presidential election will be decided, according to conversations with several Trump and Democratic campaign staffers.

In addition to the key purple states — Michigan, Pennsylvania and Wisconsin — that both sides recognize as targets, the Trump campaign has its sights set on Minnesota, Nevada, New Hampshire and New Mexico, all states Trump lost in 2016, several campaign officials said.

"We are trying to actively expand the map — aggressively," one official said. "These 4 states in particular are all areas [Trump campaign manager Brad] Parscale is set on winning."

The official added that the campaign, which is planning to beef up its communications and rapid response team with additional hires before the end of the year, will soon be flooding these states with stories that don’t get a lot of attention at the national level — such as Trump's work on opioids and the U.S.-Mexico-Canada trade deal.

"President Trump will again win the states he carried in 2016, and we believe there are a number that he can add to his column in 2020," said Tim Murtaugh, director of communications for the campaign.

Meanwhile, Democrats are hoping they can pick up Florida, North Carolina, Arizona, Texas and Georgia, per talks with campaign aides and Democratic strategists.

"The midterms were a strong indicator of the Dem energy in these states, particularly in Arizona, Florida and Texas, and set the groundwork for us to flip them," one Democratic strategist said.

strategist said. Note, however, that Trump still has a positive approval rating in Texas and Georgia, even though it's smaller than it used to be. "We dream that the Democrats think they can get Texas. It's a total fantasy," one Trump campaign official said.

A Trump campaign adviser also conceded that Arizona in particular will be tough for Trump to hold onto, but pushed back on putting too much stock in the 2018 election results: "Midterms don’t mean s---. It's a midterm turnout versus a general election — totally different."

Several aides on both sides of the aisle agree that it's far too early to assume either side has any of these states in the bag and that polls can only tell you so much this far out.

The bottom line: Both Republican and Democratic campaign aides privately acknowledge that they expect the election to be razor-thin in many of these states, just as it was in 2016.

However, the Trump campaign is betting on the Republican National Committee's data prowess and the size of the Democratic field to give them the upper hand, even with Trump's approval rating underwater in nearly every key state.

Meanwhile, the Democratic National Committee's director of battleground state communications, David Bergstein, tells Axios that the Trump campaign "doesn't have a realistic argument about their map," noting that a Republican hasn't won in many of the states the campaign is targeting in over a decade.