Sen. Roy Blunt (R-Mo.) talks with reporters following the weekly Republican Senate policy luncheon at the U.S. Capitol on April 26. Blunt is facing a tough challenge from Missouri Secretary of State Jason Kander (D), who has taken aim at Blunt’s ties to party leaders, corporate lobbyists and, now, Donald Trump. (Chip Somodevilla/Getty Images)

BRIDGETON, Mo. — It was a simple question, and Sen. Roy Blunt had a simple answer.

No, the Missouri Republican told the handful of reporters gathered at an endorsement event in this St. Louis suburb, he would not attend the upcoming Republican National Convention.

The question of why proved more difficult.

“You know, I haven’t gone to the convention for more than a day or two in a long time,” Blunt said, adding that his primary election is two weeks later.

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But, a reporter asked him, has he ever skipped one entirely?

A long pause ensued. “You know, I’d have to think through the conventions,” Blunt said. “I know I didn’t go to San Diego,” in 1996.

“Conventions,” he added a moment later, “have never been very appealing to me.”

And that tortured answer came the day before Donald Trump clinched the GOP presidential nomination with victory in the Indiana primary.

Some Republicans in Congress could be at risk of losing seats, in part because of the party's controversial presidential candidate Donald Trump. These are some the Republicans who are feeling the "Trump effect" the most. (Deirdra O'Regan/The Washington Post)

Trump’s unexpected ascension has forced Republican lawmakers across the country — most of whom, like Blunt, have pledged to support their party’s eventual nominee — into verbal contortions as they try to distance themselves from Trump’s divisive antics without alienating the millions of GOP voters who nominated him.

That dynamic — now certain to play out for another six months — has Democrats increasingly confident about their chances to win back the Senate majority in 2017.

Because of Trump’s candidacy, national Democrats believe they can expand their Senate map beyond the battleground states like Illinois, Wisconsin, Ohio and New Hampshire to win the five seats they need. Key forecasters now think Republican incumbents in states like Arizona, North Carolina and Missouri, considered safe a year ago, are now vulnerable.

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“If Donald Trump is at the top of the ticket . . . no doubt that this may be the race of my life,” Sen. John McCain (R-Ariz.) said at a closed-door fundraiser last month, according to a recording published last week by Politico.

It remains unclear whether Trump could lose Missouri, a state that, four years ago, preferred Mitt Romney by 10 points. But Democrats believe Blunt is vulnerable in any scenario and have recruited a particularly potent challenger in Jason Kander, the 35-year-old Missouri secretary of state, a former Army intelligence officer who served in Afghanistan and is now waging an aggressive campaign targeting Blunt’s longstanding ties to corporate interests and his party’s Washington leadership.

“If you were going to go into a lab and build out of spare politician parts what people are angry about in Washington, you would build Roy Blunt,” he said.

Blunt has been in politics since 1972, when he served as the campaign driver for John Ashcroft, the future U.S. attorney general, during an unsuccessful House bid. In 1984, Blunt was elected to first of two terms as Missouri secretary of state — the first Republican to hold the office in decades — and in 1996, he won a House seat and rose quickly through the GOP ranks.

Blunt became acting majority leader in 2005, after Rep. Tom DeLay (R-Texas) stepped down due to a corruption indictment. He was unexpectedly beaten months later in a secret-ballot election for top party leader by Rep. John Boehner (R-Ohio), who would go on to become House speaker. He won a Senate seat in 2010, and Blunt has maintained his leadership ambitions there: He now serves as vice chairman of the Republican conference.

Politics is undoubtedly the Blunt family business: His wife, Abigail, is the top D.C. lobbyist for Kraft Foods. His son Matt served one term as Missouri governor and now leads the main lobbying group for Detroit automakers. Son Andy and daughter Amy are both lobbyists in Missouri; Andy is managing his father’s Senate campaign.

While Republican voters are revolting against Washington insiders, Blunt has tended his home-state politics carefully and managed to avoid a serious primary challenge. Meanwhile, only one congressional incumbent — Rep. Chaka Fattah (D-Pa.), tarnished by scandal — has been defeated so far in the congressional contests.

During his most recent campaign swing, Blunt did not pretend to speak the language of an outsider — opting instead for talk of economic opportunity and “runaway regulators” in Washington, railing against new sets of environmental and labor rules issued by the Obama administration.

During a morning drive-time interview Tuesday on St. Louis’s KTRS-AM, Blunt diagnosed the political mood this way: “People are angry, they’re concerned, they’re beaten down by the regulators, and it’s been hard to look up.”

Kander’s campaign, meanwhile, is delivering some of the most aggressive attacks Blunt has ever faced.

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For the first time in his career, Blunt has faced questions about his Vietnam-era draft record and he has also been put on the defensive over his ties to former House Speaker Dennis Hastert. After Hastert admitted to child molestation in court last month, Blunt donated $11,000 to offset contributions he’d received from Hastert’s political action committee between 2009 and 2013.

Perhaps most shockingly to observers in D.C. and Missouri: Kander narrowly outraised Blunt in the most recent fundraising quarter, raising GOP concerns about Blunt’s readiness for a tough race.

Public polls have shown Blunt leading Kander in a head-to-head matchup, but the surveys show that Kander is still relatively unknown, while Blunt is both well-known and viewed unfavorably by a plurality of likely voters.

Amid a barnstorming tour of the state last week, conducted by charter jet to promote his endorsement by the U.S. Chamber of Commerce, Blunt said he was confident his campaign was on track and betrayed little concern that the anti-establishment mood could hurt his chances.

“This Senate race is about this Senate race,” he said, dismissing the suggestion that Republicans need to change their playbook in 2016: “The rules of hard work in politics always work.”

Blunt steered clear of the presidential race in his campaign appearances, and, in an interview, he pointed to his close watch on state concerns.

That includes his effort to bring medical research funding to the state and his recent role in keeping a major federal facility — the western headquarters of the National Geospatial-Intelligence Agency — from leaving St. Louis. He also plays up his ability to work with his colleagues — pointing to attempts to pass mental-health legislation and secure funding to combat the Zika virus.

“I’m a conservative guy who can still get things done,” he said. “I’m both willing to do hard things and someone that people turn to when hard things need to be figured out.”

Blunt also said he would be able to draw a sharp contrast with Kander based largely on his opponent’s four years as a state legislator.

“On the very basic philosophy of government, you can look at my record and you can look at his record, and they are dramatically different,” he said. “I’d be more concerned in explaining that choice if he didn’t have a voting record.”

Both Blunt’s campaign and the National Republican Senatorial Committee have moved more decisively in recent weeks to highlight Kander’s liberal votes on health care, environmental regulations and gun control. They have also seized on Kander’s record as secretary of state, highlighting critical details from a financial audit and seeking to tie him to election problems during the March presidential primary.

And they are trying to turn Kander’s anti-insider message against him. One NRSC web ad highlighted his campaign trips to D.C. with a dancing panda “pandering to big-money Democrats and lobbyists” to raise money.

Kander said he’s already proven he can withstand Republican attacks on his legislative record in winning his 2012 race, which made him the youngest statewide elected official in the nation. “If Roy Blunt wants this campaign to be a debate about who’s more Washington,” he said. “I think that would be a great debate for us to have.”

Blunt holds a deeply conservative voting record but does not readily serve up red meat on the campaign trail, either by attacking Kander or by seizing on the most pointed issues of the GOP presidential race — whether a border wall or transgender access to bathrooms.

Kander, meanwhile, has trained his message on middle-class economic concerns: raising the minimum wage, making college more affordable. And, notably, he has sought to plant a wedge between Blunt and Trump on foreign trade, a cornerstone of the presumptive presidential nominee’s appeal.

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Where Trump is a fierce critic of free trade, Blunt has voted to support it since joining Congress in 1997. Last year, he voted to grant the president fast-track negotiating authority to finalize the sprawling Trans-Pacific Partnership with 11 other Pacific Rim nations and says he will support the deal when it comes to Congress.

Kander came out early against the TPP, and he paid a visit last week to a union hall outside Kansas City, where he sat down at a table with labor leaders and heard their misgivings about trade deals.

“This issue right here, there’s a big difference,” said Eric Hall, president of the United Auto Workers local representing 8,100 workers at the Ford truck plant across the road. “They’re on opposite sides, and our members are going to eat this up. To be quite honest with you, this is their livelihood.”

A day earlier, the U.S. Chamber’s national political director, Rob Engstrom, adopted the attack-dog role as he delivered Blunt his organization’s endorsement in Scott City, in the state’s conservative southeast corner.

Engstrom said Kander “is fundamentally and clearly another vote for the Harry Reid, Nancy Pelosi, Barack Obama agenda” and “completely unprepared to be a United States senator.”

The escalating attacks by Blunt’s allies on Kander is a sign his campaign is taking things more seriously.

“In a normal election year, he would be untouchable,” said Jay Knudtson, former Republican mayor of nearby Cape Girardeau, after the event. “But given the volatility and the uncertainty, he’s aware he can’t take anything for granted.”

Blunt has nearly double Kander’s war chest, according to the candidates’ most recent disclosures — $5.4 million versus $2.8 million. And he can likely rely on another advantage this year: Major GOP donors dismayed with Trump are likely to funnel money down-ballot that otherwise would have been spent on the presidential race.

“There’s going to be a significant number of traditional Republican donors who are looking toward the Senate as the best investment they can make in 2016, and I think candidates across the board will be happy to have the help,” said Josh Holmes, a Republican strategist and a former top aide to Senate Majority Leader Mitch McConnell (R-Ky.).

Blunt can also take some succor from recent history: Presidential landslides have not necessarily translated into significant Senate swings.

Barry Goldwater’s massive 1964 loss was accompanied by a Democratic gain of only two seats. Democrats actually picked up two seats in both 1972, as Richard Nixon cruised to a second term, and in 1984, when Ronald Reagan was re-elected in a landslide.

Blunt himself pointed to the 2012 result in Missouri — when senior senator Claire McCaskill, a Democrat, won by 15 points as Romney cruised — as evidence that his fate won’t be tied to Trump’s.

But Kander said if tickets were going to be split, they would splitting in his favor: “If Senator Blunt is counting on people to vote for Hillary Clinton and for Senator Blunt, I’ve been to every county in Missouri over the past six months, I’ve met a lot of people, and I haven’t met that person.”

Correction: A previous version of this article misreported Kander’s campaign cash balance. He reported having $2.8 million cash on hand and the end of the last fundraising quarter.