An independent super PAC aligned with Heritage Action for America, the political arm of the conservative Heritage Foundation, launched a seven-figure ad buy in the Arizona Senate race after GOP leadership pulled more spending from the key contest.

On Tuesday, the Sentinel Action Fund announced another $1 million-dollar spending campaign to support venture capitalist Blake Masters in his bid to unseat incumbent Democrat Sen. Mark Kelly.

The 30-second ad features former Obama Border Patrol Director Mark Morgan highlighting Kelly’s embrace of open borders under President Joe Biden. Morgan served as acting commissioner of U.S. Customs and Border Protection for President Donald Trump and is now a visiting fellow at the Heritage Foundation.

“Today, the cartels call the shots,” Morgan said. “Joe Biden’s weakness threatens Arizona, and Mark Kelly is his enabler.”

According to a tracker from FiveThirtyEight, Kelly has voted with President Biden more than 94 percent of the time, making the Arizona senator one of the administration’s reliable allies in the split chamber.

In the Sentinel Action Fund’s latest ad, Morgan hammered Kelly’s votes on immigration. Kelly rejected reinforcements at the border, opposed more equipment for drug detection, and voted to end Trump’s “Remain in Mexico” policy. Masters, on the other hand, has made border security a pivotal part of his platform, earning the endorsement of the National Border Patrol Council.

“Arizonans deserve to know the truth,” Jessica Anderson, the president of the Sentinel Action Fund, told The Federalist. “Senator Mark Kelly has a long track record of enabling President Biden’s failed border policies. He has failed to support Border Patrol and give our law enforcement the tools they need to end the waves of drugs and crime coming over the border into Arizona.”

The influx of cash follows a mid-season announcement from Senate Minority Leader Mitch McConnell withdrawing more resources from the western battleground seen as critical in reclaiming the upper chamber majority. The move is a clear play by McConnell to aim for a minority he can control as opposed to a majority that threatens his perch in Senate leadership. During the Republican Senate primary, Masters pledged not to support the octogenarian lawmaker for another term as GOP leader.

[RELATED: McConnell Dumps Another Million Into Alaska To Save Murkowski After Ditching Arizona’s Blake Masters]

In late September, McConnell’s Senate Leadership Fund canceled nearly $10 million worth of planned television spending set to boost Masters.

“The cancellations mean that the GOP’s leading super PAC won’t be spending any money in Arizona, one of the most closely watched Senate races in the country,” Axios reported. The move left Masters, buoyed by GOP megadonor Peter Thiel in the primary, left to fill the gap on his own. McConnell’s allies, the paper reported, are “confident that other outside conservative groups will make up much of the difference.”

The top GOP leader’s September pull-out followed one in August when McConnell axed $8 million from the contest. It was two weeks after that announcement the Sentinel Action Fund also stepped in with a $5 million-dollar campaign to bolster Masters.

“We know that this is absolutely a winnable race,” Anderson told The Federalist. “Sentinel Action Fund is going to keep investing and fighting through Election Day. Every part of the conservative coalition should join us and win this vitally important race.”

According to RealClearPolitics’ latest aggregate of polls, which are often manipulated to inflate support for Democrats, Masters remains within four points of the Democrat incumbent. In 2020, Biden carried Arizona by fewer than 11,000 votes, and the state has not been represented by two Democrats in the upper chamber for nearly seven decades.

Since McConnell began to abandon the ripe opportunity for a key Senate pick-up, other groups have pitched in to pull Masters across the finish line. The Women Speak Out PAC, an affiliate of the Susan B. Anthony Pro-Life America group, launched a million-dollar ad campaign to highlight Kelly’s extremism on abortion. The Frontiers of Freedom Action (FFA) super PAC also announced a six-figure ad buy backing Masters. The National Republican Senate Committee (NRSC) led by Florida Sen. Rick Scott, who feuded with McConnell over “candidate quality” this summer, has also poured more money into the Arizona Senate race than any other battleground this fall.

Together, however, the groups’ collective spending to date remains far less than the $18 million McConnell stripped from the contest.

Tristan Justice is the western correspondent for The Federalist. He has also written for The Washington Examiner and The Daily Signal. His work has also been featured in Real Clear Politics and Fox News. Tristan graduated from George Washington University where he majored in political science and minored in journalism. Follow him on Twitter at @JusticeTristan or contact him at Tristan@thefederalist.com.