Less than a year out from Election Day, Senate Republicans are nervously watching the twists and turns of the presidential primary, worried it could cost them their majority in November.

Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE (R-Ky.) has made it his strategy to focus voters’ attention on this year’s accomplishments of Congress and away from the presidential circus.

He’s going to try to do that again in 2016 even though election years are not usually productive on Capitol Hill and media attention will be riveted to the campaign trail.

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“What I want to do is concentrate on what we have done for the American people. The Senate is back to work,” he told CNN’s Jake Tapper when asked about the presidential race.

McConnell will try to make Senate Republicans their own story next year.

“I don't think we ought to take the view that we're not gonna do much next year simply because there's an election,” he told reporters on Capitol Hill.

Senate Republicans are careful not to criticize the leading candidates publicly, but they’re creating distance, knowing the battle for the Senate will be won or lost in moderate swing states such as Colorado, Florida, Ohio, Wisconsin, Nevada, New Hampshire and Pennsylvania.

The worst-case scenario for Republicans would be if Donald Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE, the front-runner for months now, were to win the GOP nomination, say GOP strategists. But Sen. Ted Cruz Rafael (Ted) Edward CruzLoeffler calls for hearing in wake of Netflix's 'Cuties' Health care in the crosshairs with new Trump Supreme Court list 'Parks and Rec' cast members hosting special reunion to raise money for Wisconsin Democrats MORE (R-Texas) atop the ticket wouldn’t be much better.

They fear either candidate would turn off independent voters and energize liberals to show up to the polls.

“Every Republican who is up in 2016 is as nervous as a Christmas goose and hopeful that somehow Trump is eliminated one way or the other as early as possible in 2016 and that Cruz ultimately is not the nominee either,” said Ross K. Baker, a professor of political science at Rutgers University. “There’s a great deal of wishful thinking going on that there will be some kind of intervention that will spare them.”

Political handicappers, such as Jennifer Duffy, senior editor of the Cook Political Report, still give Republicans a slight edge because they have strong incumbents running a healthy four-seat majority, but much depends on the outcome of the tumultuous White House race.

“I don’t see their path to keeping the majority if he is the nominee,” Duffy said of Trump, adding that it would also be “problematic” if Cruz were the nominee.

“When we know the nominee we can assess those odds better than we can now,” she said.

Duffy says that “right now, with all things being equal,” Democrats have a “less than fifty-percent” chance of winning back the Senate.

Republicans hold a four-senate margin. If they lose the race for the White House, Democrats would recapture the upper chamber with a net gain of four seats because the president’s party casts the tie-breaking vote in a 50-50 Senate.

Democrats are trying to tie vulnerable Senate GOP incumbents to Trump and Cruz in a bid for swing voters.

“These candidates are still saying they will support Donald Trump if he’s the nominee. Trump’s toxic and offensive rhetoric is a serious problem for Republicans down ballot,” said Sadie Weiner, spokeswoman for the Democratic Senatorial Campaign Committee (DSCC).

“Even if they say they disagree with one or two of his policy positions. The Republican Party has become the party of Trump and if it’s not the party of Trump, then it’s the party of Ted Cruz, which Republicans seem just as concerned about,” she added.

Alleigh Marre, Weiner’s counterpart at the National Republican Senatorial Committee (NRSC), emphasized McConnell’s track record of getting major legislation, such as the omnibus spending bill and a $680 billion tax deal through the Senate.

"Republicans are entering 2016 with an advantage [Senate Democratic Leader] Harry Reid Harry Mason ReidSenate Republicans signal openness to working with Biden Mellman: The likely voter sham Bottom line MORE [Nev.] could never offer Democrats — a working Senate majority and the results to show for it,” she said.

GOP strategists say candidates who perform the best against Hillary Clinton Hillary Diane Rodham ClintonBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Virginia Democrat blasts Trump's 'appalling' remark about COVID-19 deaths in 'blue states' The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE, the likely Democratic nominee, in hypothetical head-to-head polls will help Senate candidates the most.

Recent polls by CNN/ORC and Public Policy Polling, a liberal-leaning firm, show Florida Sen. Marco Rubio Marco Antonio RubioHillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Intelligence chief says Congress will get some in-person election security briefings Republican Senators raise concerns over Oracle-TikTok deal MORE beating Clinton in a general election and Trump losing, both by a few points. The CNN/ORC poll had Cruz edging Clinton, and the PPP survey showed him losing by two points.

Democrats see the Illinois seat held by Sen. Mark Kirk Mark Steven KirkLiberal veterans group urges Biden to name Duckworth VP On the Trail: Senate GOP hopefuls tie themselves to Trump Biden campaign releases video to explain 'what really happened in Ukraine' MORE (R) as their most likely pick-up opportunity followed by the Wisconsin seat held by Sen. Ron Johnson Ronald (Ron) Harold JohnsonGOP senator blocks Schumer resolution aimed at Biden probe as tensions run high The Hill's 12:30 Report - Presented by Facebook - Big 10 votes to resume football season GOP votes to authorize subpoenas, depositions in Obama-era probe MORE (R), where Democrat Russ Feingold is ahead in polls by 10 points.

Florida, Ohio, New Hampshire and Pennsylvania fall into the next tier of likely pickups, with no obvious ranking among them. The third tier of possible Democratic pickups include North Carolina and Missouri.

Republicans meanwhile have a chance to capture Democratic seats in Nevada, where Reid is retiring, and Colorado, where incumbent Sen. Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (D-Colo.) has weak job approval numbers.

But Trump is providing a challenge to Senate Republicans.

McConnell distanced his conference from Trump earlier this month when, following a meeting with colleagues, he panned as “inconsistent with American values” Trump’s proposal to bar Muslims from entering the country.

Sen. Rob Portman Robert (Rob) Jones PortmanRomney undecided on authorizing subpoenas for GOP Obama-era probes Congress needs to prioritize government digital service delivery House passes B bill to boost Postal Service MORE (R) of Ohio, who is in a close race with former Gov. Ted Strickland (D) said in September he intends to support the GOP nominee.

“I think the country’s in trouble, and I think if we don’t have new leadership and new policies, it’s hard to imagine it getting back on track,” he told The Hill, noting that electing Hillary Clinton or another Democrat would not bring about such a change.

This month he said Trump’s proposed Muslim ban “runs counter to our traditions.”

Sen. Kelly Ayotte Kelly Ann AyotteBottom line Bottom line Bottom Line MORE (N.H.), another vulnerable Republican who also says she’ll support the eventual nominee, has called a religious test for immigrants and visitors “inconsistent” with the First Amendment.

Republican strategists don’t expect Trump or Cruz to perform well in swing states in the general election and warn they could hurt Republican candidates down-ballot if they alienate independents and moderates.

“To the extent you have a candidate at the top of the ticket that has trouble competing in states that are purple states, that affects the entire ballot,” said Josh Holmes, a GOP strategist and former senior aide to McConnell.

McConnell said something similar before Congress adjourned for the year, warning, “Unless the nominee for president can carry purple states, he’s not going to get elected.”

GOP strategists, however, argue Trump and Cruz, or any other candidate with an unproven ability to win over swing voters, won’t inflict any lasting damage on the party if they fail to clinch the nomination.

“I don’t think the damage is done at all. A lot of it remains to be seen in who the ultimate nominee is. I don’t think primary wrangling has much impact on a general election down-ballot,” Holmes said.

“It certainly matters who the nominee is. If you’ve got a nominee that can’t compete in critical states, they’re not only not going to win the presidency but they’re going to drag the entire party down,” he added.

The good news for Republican incumbents is political experts view them as having an advantage over Democratic challengers on national security issues, which are becoming increasingly prominent.

Ayotte is a member of the Armed Services and Homeland Security Committees; Johnson is the chairman of the Homeland Security panel; Kirk is a former naval intelligence officer; Portman is a member of Homeland Security; and Sen. Richard Burr Richard Mauze BurrRep. Mark Walker says he's been contacted about Liberty University vacancy Overnight Defense: Trump rejects major cut to military health care | Senate report says Trump campaign's Russia contacts posed 'grave' threat Senate report describes closer ties between 2016 Trump campaign, Russia MORE, who could face a tough race in North Carolina, is chairman of the Senate Intelligence Committee.

“Democrats are flailing as they try to separate themselves from the toxic Obama/Clinton foreign policy 'strategy' that has threatened not only our nation's standing on the world, but our security at home," the NRSC’s Marre said.

“If [the election] turns on the war on ISIS, the president’s job performance on that is 60-percent negative and Hillary, except on a couple of small matters, is pretty much in line with what the president has done and she’s an architect of some of the earlier policies,” said Terry Madonna, director of the Franklin and Marshall College Poll based in Pennsylvania.

He said that could eclipse whatever damage some GOP strategists think Trump or Cruz may be inflicting on the party brand.

“That’s going to be transcendent. The direction of the country. The nature of President Obama’s job performance,” he said.