From the White House to the campaign trail for the Democratic presidential nomination, politicians have found a popular punching bag in Amazon, accusing the retail giant of paying subsistence wages to warehouse workers while dodging taxes.

That’s one reason Amazon has aggressively courted members of Congress to walk the floors of its vast warehouses, afterward noting those visits on its social media accounts. Like last Thursday, for example, when the Twitter account for the company’s policy arm retweeted a post from Sen. Marsha Blackburn (R-Tenn.), noting her “great” tour of Amazon’s warehouse in Chattanooga.

Blackburn has been a critic of big tech and chairs the Senate Judiciary Committee’s tech task force, which is looking at privacy, data security, censorship and antitrust. Her spokeswoman did not respond to a request for comment.

For years, critics have accused the company of underpaying and overworking warehouse employees. In the United States, Amazon employs about 250,000 typically hourly workers, many of whom perform strenuous and mundane jobs such as walking many miles a day, picking items off shelves or packing up boxes. In response, the online retail giant has started a campaign to try to turn the tide — particularly as regulators take a closer look at the company for possible abuse of power.

The efforts, though, haven’t seemed to tone down the political rhetoric.

(Amazon founder and chief executive Jeff Bezos owns The Washington Post.)

The company unleashed a squad of warehouse workers on Twitter about a year ago to rebut the narrative of harsh working conditions. “FC Ambassadors,” who have written that they tweet during their shifts, have opposed unionization efforts, and one even noted that he can “use a real bathroom when I want.” Some of the tweets have been ridiculed on social media for their bot-like responses.

Amazon also caught heat last year when raising its minimum wage to $15 an hour after facing criticism from politicians and others for low payincluded plans to take away some bonuses and stock grants for warehouse workers.

That move came shortly after Sen. Bernie Sanders (I-Vt.) introduced the Stop Bad Employers by Zeroing Out Subsidies Act, or Stop BEZOS Act, which would require large employers such as Amazon to pay the government for food stamps, public housing, Medicaid and other federal assistance their workers receive. The bill currently sits in the Senate Finance Committee.

Amazon has come under fire from other politicians, as well, including Sen. Elizabeth Warren (D-Mass.), a presidential candidate. She has called for breaking up Amazon, as well as tech giants Facebook and Google parent Alphabet, claiming their anti-competitive conduct thwarts rivals and harms innovation. President Trump has spoken out several times against Amazon and Bezos, most recently instructing newly installed Defense Secretary Mark T. Esper to reexamine the awarding of a major military contract over concerns that the deal would go to Amazon’s cloud-computing division.

Amazon has increased efforts to push back against its critics, including offering tours at 23 warehouses in the United States to let visitors see firsthand how its facilities operate. The company said more than 150,000 people have toured this year, including more than 560 federal, state and local policymakers and their staffs, a pace that is likely to far surpass the number of visits it had last year. And with Congress now on its summer break, the company has welcomed a bevy of politicians to warehouses nationwide in recent weeks.

Politicians often visit local employers during their breaks, something that allows them to hobnob with constituents, learn more about the company and promote their agenda.

Rep. Susan Wild (D-Pa.) said she decided to visit an Amazon warehouse outside Allentown, Pa., on Aug. 14 to learn more about the operation. That operation came under fire eight years ago after an investigation of working conditions by the local Morning Call newspaper found ambulances parked outside during heat waves waiting to treat employees suffering from heat stress.

Despite the hot day, the warehouse was comfortable inside during her visit, she said. Amazon’s public policy Twitter account spotlighted her visit, but it “should not be construed as an endorsement,” Wild said. And she didn’t tweet about the tour, even though she did post pictures to her Twitter account of her visit the next day to HindlePower, a manufacturer in Easton, Pa.

Amazon spokeswoman Jodi Seth defended the company’s safety record and noted that, in addition to a $15 minimum wage, the company provides health and retirement benefits.

“We encourage policymakers and the general public to tour our facilities because we want them to see all of this for themselves,” Seth said in a statement.

When politicians do pose for photos at the facilities, Amazon is quick to note it. Like on Aug. 13, for example, when Sen. Cory Gardner (R-Colo.) donned a neon yellow safety vest and boxed a few items at an Amazon fulfillment center near Denver.

“It was a pleasure hosting @SenCoryGardner at our #DEN3 fulfillment center today,” Amazon tweeted from its Twitter public policy account, including pictures of the senator with company employees.

Gardner stayed mum on Twitter about his Amazon tour, even though he tweeted about visits to Maxar Technologies in Westminster, Colo., and Swisslog Healthcare in Broomfield, Colo., the same day. Gardner spokeswoman Annalyse Keller declined to comment.

Although it’s somewhat routine for politicians to drop by Amazon operations, the calculus of those visits has changed as political pressure on Amazon mounts. Rep. Ilhan Omar (D-Minn.) tweeted about a visit to a warehouse in March, although last month she pushed for an investigation of warehouse conditions, saying on Twitter that warehouse workers have died on Amazon’s watch. Amazon’s Seth said Omar’s tweet is not an accurate portrayal of activities in the company’s warehouses.

Sen. Cory Booker (D.-N.J.), who is running for president, posed with a passerby in front of Amazon’s headquarters during a visit last year but during a presidential debate lumped the retailer with Halliburton among companies “that pay nothing in taxes.” Seth declined to comment on Booker’s statement.

The spate of warehouse visits hasn’t toned down any of the opprobrium from Amazon’s fiercest critics. Sanders, who is also running for president, had said he would visit an Amazon fulfillment center. But in his ongoing sparring with the company, he has said he’s “not interested in a photo op at an Amazon warehouse.”