Why Bill Clinton Is Becoming a Bigger Target for Donald Trump "When they attack me, I'm going to attack them," Donald Trump says.

 -- Presumptive Republican nominee Donald Trump is once again attacking former President Bill Clinton, but his jabs are fueled this time by Hillary Clinton’s public speculation about her husband’s role in her administration if she wins the White House.

During a Kentucky campaign blitz Monday, Democratic front-runner Hillary Clinton said her husband would "be in charge of revitalizing the economy.”

“He knows how to do it,” she said, “and especially in places like coal country and inner cities and other parts of our country that have really been left out.”

Less than 24 hours later, Trump took to Twitter, questioning Bill Clinton’s role in the North American Free Trade Agreement, which he signed into law in 1993.

Though Trump may be turning up the volume on his attacks on the former president, the GOP candidate’s criticisms are not entirely new. Even before the first primary votes were cast, Trump was attacking both Clintons.

“[Bill Clinton] was impeached. Not allowed to practice law ... There’s things going on there,” Trump said during an appearance on MSNBC’s “Morning Joe” in January. “It’s fair game. When they attack me, I’m going to attack them. If they don’t, I would leave it off the table.”

Shortly after those remarks, Trump’s campaign posted a video to the billionaire’s Instagram page titled “Hillary and Her Friends” and showed a picture of Bill Clinton and Monica Lewinsky, the former White House intern with whom he said he had an “inappropriate relationship.”

More recently, after Trump lashed out at GQ magazine for its harsh piece on his wife, Melania Trump, ABC News asked him whether, since he says spouses should be off limits, that includes Bill Clinton.

“It depends if he's involved in the campaign. I think if he’s involved in the campaign, he shouldn’t be. And I — he probably will be involved. I think he gets involved when she plays the women’s card,” Trump said.

Meanwhile, the Clinton campaign has been deploying the former president on the campaign trail and as a fundraiser. Hillary Clinton spokesman Nick Merrill told reporters Monday she hasn’t formally decided on the shape of Bill Clinton’s role at the White House if she is elected president.

“He has a lot of creativity and knowledge to bring to bear, particularly when it comes to the economy, and she has said many times in the past that when it comes to revitalizing certain regions or certain sectors — she specifically mentioned coal and manufacturing — that she would certainly want his advice and counsel,” Merrill said.

The campaign has made it known that Hillary Clinton is not worried about Trump’s attacks. Trump’s name-calling last week was an attempt to change the subject, Merrill said. “Hillary Clinton doesn't care what he says about her,” he added. “She will continue to call him out for his outrageous positions and divisive comments.”

After Trump at an Oregon campaign rally earlier this month called Hillary Clinton a “total enabler” of her husband’s indiscretions, she avoided engaging in direct retaliations. She told reporters that she would fight his rhetoric with positivity.

“I’m going to let him run his campaign however he chooses,” she said. “I’m going to run my campaign, which is about a positive vision for our country, with specific plans that I think will help us solve problems that we’re facing, knocking down those barriers that stand in the way of people. I am going to continue to really reach out to people, to listen to people and to make the case for the kind of president that I would be.”

For his part, Bill Clinton, has largely echoed those sentiments on the campaign trail for his wife. And he repeatedly said that Republicans had historically praised her but have spent the past four years running a smear campaign.

“I actually feel bad for all of these Republicans because their greatest achievement was they kept anything from happening,” he said to a group of supporters in Frankfort, Kentucky, last week.

The former president, however, has engaged in subtle attacks on Trump, most recently mocking the GOP front-runner’s campaign slogan. “Let me tell you something. I was in the heart of coal country, in eastern Kentucky, last night, and there were a bunch of people that were booing when I came there,” he said.

“And I said, ‘Look, you’ve got two choices here. If you believe things should be made as they once were, which is essentially make America great again, right? No, wait, wait — once were. Remember this: It wasn't so great for a lot of people, the way things once were.”