NEW YORK — No presidential candidate in modern history has behaved like Donald Trump. And that distinction, paradoxically, might be enough for Republicans in the House of Representatives to keep their majority in November.

Outside Trump’s campaign, Republican strategists are resigned to the likelihood that Hillary Clinton will keep the White House in Democratic hands. The scramble to defend their Senate majority, perilous with any Republican nominee, has grown increasingly difficult.

But there’s little sign that the party’s majority in the House is in jeopardy. Democrats need a 30-seat gain to snatch the speaker’s gavel. That would require Democrats to win nearly all the Republican seats for which they are even in striking distance now.

David Wasserman, an analyst of House elections for The Cook Political Report, sees that as a sign that Republican voters have separated their judgment of the party’s nominee from its candidates for the House.

“Trump is such a unique candidate,’’ Wasserman said of the self-described billionaire, who has feuded with the media and political adversaries from both parties.

Citing the past two elections in which voters flipped party control of the House, he added, “We don’t really see the groundswell of support we saw in 2006 or 2010.’’

Consider the Third Congressional District of Kansas. It includes affluent suburbs filled with the college-educated white voters that Trump has struggled to reach.

Although Republican nominee Mitt Romney beat President Obama there by 10 percentage points in 2012, Clinton is seen as having a decent shot at outpacing Trump in the district, Republican pollster Neil Newhouse said. But he added that the incumbent, Representative Kevin Yoder, a Republican and a client of Newhouse, was not nearly as at risk among those voters.

House Republicans have strong defenses in the congressional district boundaries, which set the terms of competition. Population growth among nonwhite voters, who tend to lean Democratic, occurs largely in areas where Democrats already dominate; most Republican incumbents represent districts in which voters already lean their way.

Long wary of Trump, the House speaker, Paul D. Ryan, and potentially vulnerable members of his caucus have fortified those defenses by keeping him at arm’s length.

“Not my first choice,’’ Yoder said in May, offering only a tepid endorsement of Trump.

As Trump’s poll numbers sag, other Republicans are preparing campaign arguments that assume a Clinton victory and portray themselves as a brake on Democratic excesses.

“Get ready for the fall message: can’t afford to give Hillary Clinton and Nancy Pelosi a blank check,’’ said Newhouse, referring to the Democrat who would be in line to replace Ryan as speaker.

Republicans in the Senate have tried to keep their distance, too, but their margin of error is much slimmer, and the task is more complicated. They can lose no more than three seats to assure they hold their majority, and Republicans face more diverse statewide electorates.

Seven Republican-held seats are up for election in states where Obama won twice, and other races that might ordinarily have been seen as safe bets are in play.