Hillary Clinton is seen aboard the campaign bus in Cleveland on the third day of a bus tour through Pennsylvania and Ohio.

July 31, 2016 Hillary Clinton is seen aboard the campaign bus in Cleveland on the third day of a bus tour through Pennsylvania and Ohio. Melina Mara/The Washington Post

The former secretary of state, senator and first lady is the Democratic nominee for president.

The former secretary of state visits key states in her quest to become the Democratic nominee for president.

The former secretary of state visits key states in her quest to become the Democratic nominee for president.

Congressional Democrats set out on a mission Wednesday to tie Donald Trump to every possible Republican running in competitive down-ballot races, following the real estate mogul’s elevation to the GOP’s presumptive presidential nominee.

In memos, in news releases and across social media, Democrats tried to take advantage of Trump’s unchallenged hold on the presidential nomination by linking Republican incumbents to his controversial statements and proposals on the campaign trail. Democrats believe Trump’s triumph will allow them to make electoral inroads that could flip the Senate to their control and provide major gains in the House.

“The bottom line is, the battlefield is going to shift in our favor,” Kelly Ward, executive director of the Democratic Congressional Campaign Committee, said Wednesday. Her committee issued a memo to the Colorado news media highlighting Trump’s positions and how they will play in the highly competitive race involving Rep. Mike Coffman (R), who represents Denver’s eastern suburbs. The memo was headlined “Coffman and Trump: Welcome to the Trump ticket.”

In New Hampshire, Gov. Maggie Hassan (D) is in a closely watched Senate contest with the GOP incumbent Kelly Ayotte. On Wednesday, Hassan denounced “the Donald Trump-Kelly Ayotte Republican Ticket,” in an effort to link the incumbent to Trump’s views on defunding Planned Parenthood and blocking the consideration of Supreme Court nominee Merrick Garland. That came as Ayotte, back home for the congressional recess this week, told local media that she would support but not formally endorse Trump.

Positions like those have boosted Democratic hopes. Republicans can either embrace Trump or distance themselves, but either prospect risks alienating some important bloc of voters.

Senate Majority Leader Mitch McConnell (R-Ky.), for instance, walked a fine line in a statement Friday evening that noted his previous commitment to supporting the GOP nominee without explicitly endorsing Trump or his platform.

“Republicans are committed to preventing what would be a third term of Barack Obama and restoring economic and national security after eight years of a Democrat in the White House,” McConnell said. “As the presumptive nominee, he now has the opportunity and the obligation to unite our party around our goals.”

Majority control of the Senate, which was considered a close call before primary voters starting going to the polls in February, is now getting more difficult by the week for Republicans. One analyst, Charlie Cook, now gives Democrats a 60 percent chance of reclaiming the majority.

Trump’s rise has Democratic strategists salivating at the prospect of expanding the Senate battle­ground from states that were already expected to be competitive in a place as inhospitable as Arkansas. In 2010 and 2014, well-funded Democratic incumbents could not even get 40 percent of the vote there.

Illustrating the perceived potency of a Trump nomination, Connor Eldridge, the Democratic challenger waging an uphill fight against Sen. John Boozman of Arkansas, released a lengthy web video this week that included a variety of misogynistic comments by Trump alongside Boozman’s pledge to support the eventual GOP presidential nominee. The video has drawn more than 90,000 views and media coverage in Arkansas and nationally.

Rep. Louie Gohmert (R-Tex.) said Tuesday on Fox Business that he “had no fear of losing the House until I saw” the Eldridge commercial. “This is a dangerous time,” he said.

Republicans, however, pointed to the already well-structured, well-financed campaigns that their incumbents have built in anticipation of a rocky relationship with their presidential nominee since Trump and his main rival, Sen. Ted Cruz (R-Tex.), surged to the front of the pack earlier this year.

As Donald Trump appeared to soon be the last candidate standing in the race for the GOP nomination, Democratic front-runner Hillary Clinton tweeted this video, showing Republicans launching attacks at Trump. (Hillary Clinton)

GOP strategists signaled Wednesday that they intended to run their campaigns against the likely Democratic nominee, Hillary Clinton, whose favorable ratings are at an all-time low.

“Republicans will continue to lay out their visions to help our country recover from eight years of the Obama economy and get people back to work. There is a reason Democrats aren’t lining up to campaign with Hillary Clinton. She is a toxic candidate whose failed leadership has put the security of our country at risk,” said Andrea Bozek, spokeswoman for the National Republican Senatorial Committee.

Additionally, Republican super PACs for congressional candidates will probably see their cash advantage grow as some conservatives have signaled their intention to move resources from the presidential campaign to Senate and House races.

This week, Freedom Partners Action Fund, one of several groups aligned with billionaires Charles and David Koch, unleashed a $2 million media campaign against Wisconsin Democrat Russ Feingold, a month after another Koch-aligned group, Americans for Prosperity, unveiled a more than $1 million round of ads praising Feingold’s opponent, Sen. Ron Johnson (R-Wis.)

The Senate field has been largely set for several months. The first tier of Republican seats at risk are five incumbents running for their first reelection in states that President Obama won twice, along with the seat of retiring Sen. Marco Rubio (R-Fla.). A second tier of seats includes GOP incumbents in North Carolina, Missouri, Arizona and Iowa who were once considered safe but could be in trouble depending on how Trump performs.

Democrats, facing a difficult race in one seat of their own, that of retiring Minority Leader Harry M. Reid (Nev.), need to win just four seats to claim the majority if Clinton wins the presidency.

House Democrats have been racing to confront this new reality, trying to line up candidates in districts that previously seemed securely in Republican hands.

But House Republicans dismiss claims that their majority is at risk.

“The road back to majority for House Democrats this cycle doesn’t exist, and they know it,” said Katie Martin, spokeswoman for the National Republican Congressional Committee.