Rep. Bob Dold (R-Ill.).  (Gabriella Demczuk/Getty Images)

LINCOLNSHIRE, Ill. — Candidates in any race spend a lot of time and money telling voters exactly who they are. This year, moderate House Republicans like Bob Dold are investing as much time telling voters who they aren’t — in this case, Donald Trump.

Dold — an Illinois Republican running for reelection in one of the most competitive districts in the country — may be caught in what some Republicans fear will be a powerful Trump downdraft, sinking vulnerable down-ballot Republican candidates instead of lifting them up. Though many won’t say so on the record, still hoping that anyone-but-Trump will win their party’s nod, several Republican strategists are voicing fear about the fate of the rest of their party’s candidates if the wealthy business mogul becomes the GOP standard-bearer. Some worry about a similar dynamic if Sen. Ted Cruz (R-Tex.), a hard-line conservative, nabs the nomination.

Those fears became more palpable on Saturday night when Trump won the South Carolina primary by 10 percentage points, solidifying his status as the Republican front-runner.

“I think Trump would be a disaster. I think Cruz would have a very hard time in a lot of states as well,” said Stuart Stevens, Mitt Romney’s chief 2012 strategist. Trump “has no policy. It might be fun for a day to get in a fight with the Pope but this is not a way to win a campaign.”

Stevens argues that the presidential nominating contest is a “long process” that “has to play out” and that Trump won’t ultimately win the GOP nod, nor can down-ballot Republicans be so easily linked to the controversial candidate.

“It is [an] intellectually lazy and dishonest attempt to say that just because Donald Trump is running that way that all Republicans are this way,” he said.

Unlike some other vulnerable Republicans, Dold is not waiting to distinguish himself from Trump in his suburban Chicago seat, where Democrats are likely to turn out in droves to back their presidential nominee. And it is not an idle concern that moderate Republicans — or independents who might support a Republican in another presidential year — will choose to either stay home or worse, back Hillary Clinton or Bernie Sanders.

“For me, it’s personal,” Dold said in an interview with The Washington Post. “[Trump’s] comments about women, his comments about minorities, about Latinos — for me that’s not a guy I would support.”

In a refrain that national Republican strategists may be echoing if Trump or Cruz wins the GOP nod, Dold believes the key to his reelection comes from ticket-splitters, voters who are likely to pull the lever for him and either Hillary Clinton or Bernie Sanders.

“We’ve got a long history in the 10th [district] of people looking at the House race differently than other races,” Dold said. “We have a long history of ticket-splitters.”

Still, voter turnout grows by nearly a third in presidential election years with many voters driven only by the candidate at the top.

Although the Senate — with several blue-state Republicans up for reelection and a contentious Supreme Court battle underway — may be more in play in November, fears of a Trump or Cruz nomination have started to trickle down to the more secure GOP-controlled House.

Dold is one of at least 16 vulnerable House Republicans up for reelection this year who could be endangered if Trump or Cruz  lead the ballot. Hardly anybody in Washington expects that Democrats can retake the House majority even with Trump at the top of the ticket. Republicans would have to lose more than 28 House seats and fewer than 25 of them are expected to be truly in play. The more modest hope among Democrats is that if Trump or Cruz wins the nomination, the Democratic playing field will be expanded and Republicans like Dold will be easier to defeat.

“The top of the ticket is going to have a significant impact for House and Senate races and anyone who says otherwise is kidding themselves,” said Republican strategist Brian Walsh, a former spokesman for the National Republican Senatorial Committee. “Members like Bob Dold and other moderates who disagree the most with people like Ted Cruz are the most vulnerable.”

“I think there is damage being done broadly to the Republican brand,” Walsh said of the chaotic Republican presidential primary so far. “I worry about the number of Americans who have never voted before, minorities and Hispanics. I worry about the rhetoric that is coming out from the party.”

It is possible, however — as Trump argues — that if he wins the GOP nod that new voters who haven’t gone to the polls before and some Democrats and independents may be attracted to his candidacy. That seems less probable in the case of Cruz, who has nurtured a national image as a conservative firebrand.

But national Republicans will have their eyes trained on seats like Dold’s, watching to see if Trump could hurt their vulnerable incumbents nationally.

Dold’s 10th district –which begins in the affluent suburbs just north of Chicago and stretches North to the working-class towns that hug the Wisconsin border – could not be more competitive. He won it in 2010 with 51 percent of the vote and lost it in 2012 by less than a percentage point to management consultant Brad Schneider (D) in a district that President Obama carried by 17 points.

Dold came back to Congress after the 2014 midterms, joining a House GOP majority that bickered over Planned Parenthood, immigration and other hot-button issues as well as ousted House Speaker John Boehner (R-Ohio). That leaves him tacking left on social issues and remaining to the center-right on fiscal issues in an election that may pit him against Schneider for the third time.

Dold has done what he can to separate himself from a House Republican majority that is hugely unpopular (Congress’s disapproval rating is at 77 percent, according to the Real Clear Politics average). He opposed the majority of Republicans in nearly every national political battle last year — he was one of three Republicans to oppose a bill to defund Planned Parenthood and he voted against the House-passed 20-week abortion ban. He also voted to renew the charter for the Export-Import bank and against a measure that would have gutted President Obama’s controversial clean power plan.

But Democrats are happy to lump Dold with every other Republican from Trump to House hardliners who threatened to shut down the government over funding for Planned Parenthood and backed budgets that would slash food stamps, gut Obamacare and privatize Social Security.

“Republicans can’t hide from the values and the principles that they adopt,” said Democratic Campaign Committee chairman Ben Ray Lujan (D-N.M). “That’s their vision for America. That is probably the clearest contrast that I can say.”

Last month, the DCCC included Dold in a strategy document that identified candidates who could be damaged by the rise of anti-establishment Republicans like Cruz and Trump. The memo said Trump would give Democrats the upper hand in toss-up races.

[House Democrats gleeful at rise of Trump and Cruz, predicting cost for congressional Republicans]

Dold shrugs off the political posturing, putting distance between himself and even the word Republican.

“They’re trying to talk about the Republicans, the Republicans, the Republicans,” Dold said of the attacks. “They just have to look at my record.”

Dold isn’t wrong to believe that voters in his district are less likely to be swayed by national politics than in other parts of the country. Voters here have picked Democrats for president since Bill Clinton was in office. But Schneider was the first Democrat elected to the House seat since 1979.

Dold’s seat was previously held by another moderate Republican at risk in the 2016 election, Sen. Mark Kirk (R-Ill.). Kirk won the seat in 2000, a year when 51 percent of the district voted for  Al Gore, and Kirk was easily reelected until he won his Senate seat in 2010.

Democrats have been fighting to wrest control of this seat for more than a decade and have invested significant time and money in the effort. In 2010, Democrats in the Illinois legislature redrew the district to include lower-income towns with higher minority populations. They also moved the border just enough so that Dold no longer lived inside the district.

The new Illinois 10th went from just over 4 percent African American to 8.5 percent, and the district’s Hispanic population grew from around 15 percent to over 20 percent between 2010 and 2015.

Republican strategists point out that Dold lost to Schneider by just one percentage point despite a 2012 Obama landslide here — he went on to retake the seat in 2014 despite the disadvantageous redistricting.

And some GOP strategists argue that Democrats won’t turn out in 2016 in the same large numbers as they did for Obama.

“Hillary Clinton is not Barack Obama,” said Ian Prior, communications director for the conservative super PAC American Crossroads. “She’s not going to turn out the Obama coalition or the volume of voters that Obama did. The question is what happens to that 1 percentage point [Schneider won in 2012] without that huge turnout.”

Prior and other GOP operatives say House races are typically won on local issues and through the kind of door-knocking, parade-waving grind of basic retail politics that Dold does best.

“In 2015, we did 550 events,” Dold boasted. “We did 26,000 mail contacts with folks back in the district. We’re trying to remain active.”

He also has the strategic and financial support of the party establishment. Dold is one of two dozen swing-district Republicans who signed on to be part of the National Republican Congressional Committee’s “Patriot” program, which gives vulnerable members access to targeted campaign assistance and a special pot of cash set aside to aid in their salvation.

Dold also represents House moderates on an official advisory panel assembled by House Speaker Paul D. Ryan (R-Wisc.). The honorary position may help with fiscal conservatives but it may be a major liability as Schneider and other Democrats try to tie Dold to Ryan’s deep cutting budgets and socially conservative agenda.

“I’m socially progressive and fiscally responsible,” Schneider said in an interview. “He is creating a split record.”