WASHINGTON — In two House Republican strongholds — a Georgia district sprawling from Atlanta’s exurbs to the Alabama line and another in California’s Central Valley — upcoming elections illustrate the vigilance that this antiestablishment moment demands of GOP candidates.

Dentist and former local mayor Drew Ferguson is vying for the Republican nomination in a July runoff for the open Georgia seat, calling himself ‘‘a conservative outsider’’ and boasting of spurring economic development.

He sometimes sounds like presumptive GOP presidential nominee Donald Trump, saying that border fences are ‘‘not mean-spirited’’ and supporting limits on refugee resettlement.

Yet many religious conservatives and conservative groups such as the Club for Growth prefer state Senator Mike Crane. He opposes narrow tax breaks, and he’s taken hard-line views against gay marriage and for making English Georgia’s official language.

In California, House Majority Leader Kevin McCarthy should easily dominate Tuesday’s primary. The $6.4 million McCarthy amassed for his own campaign — he’s also provided plenty more for GOP colleagues — crushes the $31,000 raised by his best-financed opponent, conservative Republican Ken Mettler.

Unforgotten is 2014, when the congressional career of the previous majority leader, GOP Representative Eric Cantor of Virginia, ended after a primary ambush by an unknown, underfunded college professor, Dave Brat, who’s now in the House.

Republicans are virtually assured of keeping the Georgia and California seats in November’s elections, but these preliminary battles underscore the stakes for the party.

Races like Georgia’s will help determine whether a fresh influx of ideological rebels will make the already rambunctious House GOP even harder for its leaders to steer, while Mc­Carthy’s contest shows a lingering unease from Cantor’s fall.

‘‘When you’re head of an organization that has a 15 percent approval rating, you worry,’’ said Tom Davis, a former Virginia representative and head of the House GOP campaign committee.

Not one House GOP incumbent has been ousted this year in primaries. Their survival has surprised some, just eight months after conservatives drove House speaker John Boehner, Republican of Ohio, into retirement, and as Trump vanquishes political professional rivals.

At least one Republican incumbent will lose Tuesday: Redrawn lines pit Representatives Renee Ellmers and George Holding against each other for the nomination in one North Carolina district. With congressional primaries remaining in more than half the states, other incumbents in Colorado, Kansas, and Oklahoma could tumble too, and groups from competing ends of the party’s ideological spectrum are engaging.

The American Action Network and Congressional Leadership Fund, aligned with party leaders, helped House Transportation Chairman Bill Shuster of Pennsylvania and Ways and Means Chairman Kevin Brady of Texas survive primary scares.

According to figures from the nonpartisan Center for Responsive Politics, the US Chamber of Commerce spent $1.8 million helping Representative Martha Roby, Republican of Alabama, defeat a Tea Party challenger in a March primary and helped an ally win the nomination for an open Kentucky seat.

On the other side, the Club for Growth spent $1.1 million to help conservative businessman Warren Davidson capture the GOP nomination for Boehner’s vacated seat, a symbolic triumph, and disbursed $800,000 against Ellmers, according to the center.

Potentially vulnerable GOP incumbents have survived primaries in Texas, Pennsylvania, Illinois, Alabama and Georgia. Party operatives credit lawmakers’ heightened attention to hometown concerns since Cantor’s defeat.

House Speaker Paul Ryan, Republican of Wisconsin, has raised more than $30 million since becoming speaker last fall, according to Spencer Zwick, his national finance chairman.

Republicans control 247 of the House’s 435 seats, including a vacancy sure to go Republican, and it’s the party’s high-water mark since 1931. But the presidential election should draw added Democratic voters, perhaps costing GOP seats.