By KIM CHANDLER, Associated Press

MONTGOMERY, Ala. (AP) — The Senate Leadership Fund on Monday reserved a $2.6 million television ad buy on behalf of U.S. Sen. Luther Strange of Alabama, bidding to ward off challengers for the seat previously held by Attorney General Jeff Sessions.

The super political action committee, which has ties to Senate Majority Leader Mitch McConnell, made the show of fiscal force ahead of an August GOP primary on which Strange will face several challengers, including former Alabama Chief Justice Roy Moore.

Senate Leadership Fund spokesman Chris Pack told The Associated Press the buy is just the start of what the group plans on spending to support the Republican senator. The ads will start July 11 and run through the Aug. 15 primary.

"A lot of people in glass houses are throwing stones in Alabama, and they will quickly realize that this won't be going unanswered. This $2.65 million buy is just an initial down payment on Senate Leadership Fund's commitment to supporting Senator Strange," Pack said.

Ever since a series of messy Republican primaries led to losses of winnable Senate races in 2010 and 2012, Republicans led by McConnell of Kentucky have worked aggressively to defeat fringe primary candidates in Senate races. Their goal has been to ensure that GOP Senate primaries produce mainstream Republican candidates who can go on to win the general election. The Senate Leadership Fund is run by a former McConnell chief of staff.

The Alabama race is expected to be contentious. But the muscle flexing by the super PAC also sends a message that the challengers to Strange should prepare for a high-spending campaign.

Strange was appointed to the Senate in February by then-Gov. Robert Bentley, who resigned last month amid fallout from an alleged affair with a top staffer. Bentley had planned for a 2018 Senate election, but new Gov. Kay Ivey, moved it up to this year, setting up what's expected to be a four-month demolition derby among Alabama's dominant Republicans.

Bentley resigned to stop an impeachment push, pleading guilty to misdemeanor campaign finance violations to end a state investigation. Challengers are expected to try to batter Strange on his connection to Bentley, since Strange was state attorney general at the time of his Senate appointment.

Three other Republicans have so far announced runs for the seat including Moore, who was suspended from his judicial duties after he urged defiance of the landmark U.S. Supreme Court decision legalizing same-sex marriage.

Party qualifying for the race runs until May 17.

While Alabama has not elected a Democrat to the U.S. Senate in more than 20 years, a number of Democrats, including at least two state legislators, are considering running.