Senate Majority Leader Mitch McConnell intends to play a central role in the midterm elections, using his affiliated super PAC to block insurgent Republicans and help his party withstand the headwinds from President Trump’s low approval ratings.

The Kentucky Republican in a late Thursday interview basked in the glow of the historic tax overhaul that cleared Congress this week. But McConnell was candid about challenges Republicans face next year, both in selling tax reform to skeptical voters and weathering a brewing political storm generated by Trump’s polarizing leadership.

“The environment today is not great, the generic ballot’s not good, and I’d love to see the president’s approval rating higher. So I think we should anticipate a real knock down, drag out — even on the Senate side,” McConnell told the Washington Examiner.

Democrats “want to have a debate over the tax bill, we’re ready for it,” McConnell added. “But that won’t be the only issue. There are a lot of different things that affect the attitude of people, some of which we won’t be able to control.”

Being trapped by flawed candidates is McConnell’s biggest concern. Lousy nominees cost the GOP winnable races in 2010 and 2012, not to mention a special election this month in Alabama that saw retired Judge Roy Moore become the first Republican to lose a Senate race in that ruby-red state in 25 years.

McConnell made clear that he and his super PAC, Senate Leadership Fund, would intervene in 2018 to protect incumbents and pick sides in open primaries to quash nationalist firebrand Steve Bannon’s promised insurrection against so-called establishment candidates, and box out candidates like Moore.

“I and my allies will make every effort to make sure we have a nominee on the November ballot who can appeal to a general election audience,” McConnell said.

Asked if the Alabama race discredited Bannon, who endorsed Moore and campaigned for him even after his campaign was derailed by multiple allegations of sexual misconduct, McConnell added: “Those political geniuses managed to elect a Democrat in the reddest state in America. I rest my case.”

McConnell’s critics, particularly in some quarters on the Right, blamed him for Moore.

They said that McConnell backed appointed Sen. Luther Strange when he didn’t have to — and then, via Senate Leadership Fund, exerted too heavy a hand in the special election primary. McConnell became the issue in Alabama, and a liability for Strange. The leader’s detractors argue the scenario could repeat itself next year and bring down GOP incumbents.

McConnell, who said he had no choice but back Strange because he was the incumbent, flatly rejected that criticism and its underlying premise.

“I’m not going to be an issue in a single race in America,” he said. “I can assure you the support of the Senate Leadership Fund is not a negative. You can ask a lot of incumbents around here whether they believe it was important to their success, and it was. And, it will be there again in 2018.”

Trump’s job approval rating has hovered around 40 percent for most of his presidency, as the Democrats have opened up a double digit lead on the generic ballot test that asks voters which party they would prefer be in control of Congress.

Senate Republicans could be insulated from these forces by a favorable map, if they can avoid messy primaries. Only about a third of all Senate seats are up for election in 2018, and several feature Democratic incumbents running in Republican-leaning states that voted heavily for Trump in 2016.

It’s in these contests that McConnell expects the tax bill to be an asset, even though it was broadly unpopular nationally as it headed to Trump’s desk. To prove his point, the leader read an outline of possible script of an advertisement that he expects will air against Democratic senators like Joe Manchin of West Virginia and Heidi Heitkamp of North Dakota.

“Here’s the commercial against Joe Manchin: ‘Head of household, family of four, making $73,000 a year, gets a $2,000 tax reduction. Now maybe Sen. Manchin that doesn’t sound like a lot of money to you, but for me it’s a 58 percent reduction in my taxes; 58 percent,’” McConnell said, playing the role of ad voiceover. “Or Sen. Heitkamp: ‘Maybe $1,300 doesn’t sound like a lot to you, but I’m a single mom with one child making $41,000 a year, and that’s a 73 percent reduction in my tax bill.’”

McConnell touted his list of top recruits in targeted Senate races as a hopeful sign that Republicans were poised to field a formidable slate that could help grow a slim majority that will stand at 51 seats after Senator-elect Doug Jones, D-Ala., takes office, among them Rep. Martha McSally in Arizona; Gov. Rick Scott in Florida; state Attorney General Josh Hawley in Missouri; and Rep. Kevin Cramer in North Dakota.

Still, McConnell cautioned his party against relying on the map to save them, recalling how good it looked for Democrats in 2010 before a GOP wave fueled by dissatisfaction with President Barack Obama flipped seven Senate seats, including in a special election in deep blue Massachusetts.

“The map doesn’t win elections,” McConnell said. “The atmosphere is not irrelevant.”