(NewsNation) — Jason Miller, a senior adviser to former President Donald Trump’s campaign, opened up on the potential impact that Trump testifying in the criminal cases against him could have on his national polling numbers.

Trump has indicated his willingness to testify in his own defense if he faces trial in any of the four cases looming over him. While Trump did not specify which cases he was referring to, his openness to testifying could have significant implications for his legal battles.

Trump’s willingness to testify follows a pattern in which his poll numbers have surged every time he has faced legal troubles. Recent national polls show Trump strengthening his lead in the race for the Republican nomination despite the legal cloud hanging over him.

During an appearance on “The Hill on NewsNation,” Miller pointed out that each attack on Trump by his opponents resulted in a boost in his popularity.

“You look at the 10 polls that have come out since this fourth indictment, seven of the ten have shown President Trump leading Joe Biden, that’s a statement,” he said.

Miller cited various recent polls, including one from Premise Data showing Trump leading Biden by six points and Echelon Insights showing Trump in the lead.

“When you start looking at the swing states, that’s where President Trump, I believe, is in the driver’s seat,” Miller said. “Don’t just take it for me, the fact that Joe Biden and the Democrats have just launched this $25 million ad by targeting states that are traditionally viewed as being more blue, Wisconsin, Michigan, Pennsylvania, reaching out to constituencies that Democrats usually take for granted.”

Miller emphasized the Wall Street Journal (WSJ) numbers on the economy and voters’ attitudes, showing that three out of four voters believe inflation is getting worse.

The WSJ poll, taken between Aug. 24-30, found that 37% of registered voters “somewhat” or “strongly” approve of Biden’s handling of the economy. A majority of the same group, 59%, said they disapprove of the president’s approach to the economy.

“If you want to know why Joe Biden spent Labor Day in Pennsylvania reaching out to union workers, it’s because he knows he’s in trouble,” Miller said.

Miller suggested that, with Trump’s substantial lead in the polls, he might not need to participate in debates unless his opponents prove their worth to be on the same stage.

“President Trump is definitely in the driver’s seat,” he said. “But as he always tells us, we’re not going to take our foot off the gas.”