Democratic outside groups are ramping up negative advertising against President Donald Trump in Pennsylvania, in an effort to weaken him in a key battleground state he won by the slightest of margins in 2016 as their own presidential primary drags on.

On Tuesday, the liberal super PAC American Bridge 21st Century said it had launched a $10 million advertising campaign in Pennsylvania, Wisconsin, and Michigan targeted at working-class voters in rural areas, who were key to Trump’s victory.

And starting next week, another Democratic super PAC, Priorities USA Action, will begin airing anti-Trump commercials on TV in the Pittsburgh, Harrisburg, Altoona-Johnstown, and Scranton-Wilkes-Barre media markets. The group has reserved about $5.9 million worth of airtime through early July, according to the ad-tracking firm Advertising Analytics.

The activity on the airwaves comes as the Democratic presidential primary shows signs it may be prolonged. Former New York Mayor Mike Bloomberg is set to make his first appearance at a debate on Wednesday night as he rises in national polls, and in surveys of states that vote in March.

Priorities USA — which has pledged to spend $150 million on the 2020 campaign before the party’s convention in July — has also booked ads in other battleground states like Florida, Michigan, and Wisconsin, the New York Times reported last month. In 2016, Priorities didn’t run its first TV ad until May.

Neither group has booked ads in the expensive Philadelphia market. Bloomberg has bought the most airtime of any candidate or outside group in Pennsylvania, having spent almost $16 million on broadcast, cable, and radio commercials, according to Advertising Analytics. The Trump campaign has spent about $500,000 on the airwaves in the state.

Trump won Pennsylvania by about 0.7% of the vote in 2016, which, along with similarly close victories in Michigan and Wisconsin, helped elevate him to the White House.

The American Bridge commercials feature self-identified Trump voters who say they have soured on the president.

“Now I voted for Donald Trump, but ever since he got in office, he’s been dividing the country,” a National Guard veteran identified only as Steve from Wayne County, says in one Pennsylvania ad. "I don’t think the president understands service. As a former soldier it’s difficult for me to criticize the man at the top, but it’s important that everybody be held to account.

“I’ll vote for more Republicans,” he says in the 30-second spot, “but not Donald Trump.”

Based on information provided by American Bridge, The Inquirer confirmed through Wayne County voting records that he voted in 2016.

American Bridge spent $4 million on a similar ad campaign late last year. One of the ads faced criticism after a TV station in Erie found that a man identified as a regretful Trump voter hadn’t actually voted in 2016.

American Bridge president Bradley Beychok said the group had “undertaken a massive and unprecedented effort to strategically target the voters Donald Trump needs most in battleground states.”

It said surveys showed the earlier ads decreased Trump’s favorable ratings and increased support for Democrats.

“With a wide-open Democratic field and a potentially months-long nominating process, we need to take the fight to Donald Trump right now," Beychok said in a statement. "We will continue to elevate the voices of local voters hurt by the president’s failed policies and broken promises, and up the ante to deny Donald Trump the swing-state margins he needs in 2020.”