Rep. Fred Upton (R-Mich.) has come under fire from conservative outside groups since a Tea Party candidate announced a run against him. Now one group is stepping in to fight back.

The American Action Network (AAN) will go on the air Thursday with a positive spot touting Upton's conservative bona fides. The buy, which includes direct mail as well as TV ads, is in the low six figures and will last six weeks. The hardline, fiscally conservative Club for Growth has already run ads blasting Upton's record.

This is not the first time the center-right AAN, headed by former Sen. Norm Coleman (R-Minn.), has stepped in to battle back against more conservative outside groups: When FreedomWorks targeted Sen. Orrin HatchOrrin Grant HatchOvernight Finance: NAFTA defenders dig in | Tech pushes Treasury to fight EU on taxes | AT&T faces setback in merger trial | Dems make new case against Trump tax law | Trump fuels fight over gas tax What sort of senator will Mitt Romney be? Not a backbencher, even day one Lawmaker interest in NAFTA intensifies amid Trump moves MORE (R-Utah) before the state's caucuses, Coleman's outfit responded by running ads on Hatch's behalf. The group also plans to help Sen. Dick Lugar (R-Ind.) in his tough primary race.

Upton faces former state Rep. Jack Hoogendyk (R) in the GOP primary. Hoogendyk almost beat him in 2010 despite spending almost no money. The district is Republican-leaning but Democrats are hopeful that if Hoogendyk wins the primary, they might be able to beat him.

The AAN has increasingly taken up the tack the Republican Party used to adopt in primaries, backing establishment choices against right-wing challenges and focusing on winning races rather than ensuring ideological purity. The group's move to help Upton is the latest sign that it will continue to step into races right-wing groups have decided to target.

Watch the AAN ad here: