The battle for control of the Senate rests on the outcome of the presidential race, strategists in both parties say.
Since 1860, no party has been able to climb out of the minority to capture the Senate during a presidential election year without also winning the White House.
Strategists say 2016 won’t be any different.
{mosads}If Hillary Clinton, the current Democratic front-runner, doesn’t win the White House, there’s little chance New York Sen. Charles Schumer (D) will become Senate majority leader in 2017.
Democrats appear well-positioned to knock off two Republican incumbents, but whether they can stretch the number of Senate pick-ups to the necessary four or five while defending two of their own vulnerable seats remains to be seen.
The election map favors Democrats. They are defending only 10 Senate seats, while Republicans are protecting 24, including seven in states carried by President Obama in 2012.
But Democrats are running against the grain of history by trying to keep the White House for three consecutive terms — a feat last accomplished by Republicans in 1988, when Ronald Reagan left office with a 53-percent approval rating. Obama’s approval rating, by comparison, stands at 45 percent, according to Gallup.
“At the end of the day, I’m a believer the biggest impact will be the presidential race,” said Steve Elmendorf, a Democratic strategist, lobbyist and fundraiser.
“Ted Strickland can beat Rob Portman if Hillary Clinton is winning Ohio. Pat Toomey, no matter how good he looks on paper and the problems we’re having with the primary, I think if you get to November and Democrats are winning Pennsylvania by a huge number, Toomey’s in a lot of trouble,” he said
“If Democrats don’t win the presidential race, I don’t think we’ll win the Senate,” he added.
The map of key Senate races largely matches up with the map of presidential battlegrounds.
Aside from Wisconsin and Illinois, where Republican incumbent Sens. Ron Johnson (Wis.) and Mark Kirk (Ill.) are fighting for their political lives in blue states, the most competitive Senate contests are in presidential swing states.
Johnson trails former Democratic Sen. Russ Feingold in Wisconsin by five points, according to a mid-August Marquette Law School poll, and Democrats predict Feingold will raise more money.
Republicans counter that Feingold is fighting against history by trying to oust an incumbent who defeated him six years earlier — something that hasn’t happened since 1934.
Kirk, meanwhile, lagged six points behind Rep. Tammy Duckworth (D-Ill.) in a late-July survey by Public Policy Polling, a Democratic firm.
But Republicans are playing up Duckworth’s primary challenge, which threatens to create a schism in the Democratic Party along racial lines. Her opposition, Andrea Zopp, is African-American.
Democrats have their next best chance for capturing GOP seats in Florida, Ohio, New Hampshire and Pennsylvania, where Clinton could drive large numbers of unmarried women and minorities to the polls.
But Democrats are facing potentially divisive Senate primaries in both Florida and Pennsylvania.
Florida presents a big opportunity, with a seat left open because Sen. Marco Rubio, the incumbent Republican, is running for president. The state has a high concentration of Hispanics, who made up 17 percent of eligible voters in 2014.
Republican Lieutenant Gov. Carlos Lopez-Cantera and conservative Rep. Ron DeSantis (R-Fla.) are running against each other in what could become a bruising contest pitting the party establishment against the Tea Party base.
Democrats have their own primary fight between Reps. Patrick Murphy and Alan Grayson, although the party establishment has lined up Murphy, who has a distinct fundraising advantage.
Florida — the third-largest state — is a big prize in the presidential race. Clinton is expected to pour resources into the state to mobilize Hispanic and African-American voters, which would help Democrats down ballot.
“It’s much more difficult [for Democrats] if Hillary Clinton were to lose her bid to be the next president of the United States. That means you’re losing electorates that can help whoever the Republican senator is. Ohio comes to mind. Florida. Those seem to be the two big ones in play,” said Mike McSherry, former deputy political director of the National Republican Senatorial Committee.
The Florida Senate primary isn’t until Aug. 30, however, so Rubio could change his mind if he’s out of the presidential race by May of next year, the state’s filing deadline.
Rubio’s spokesman, Alex Conant, ruled out the possibility.
“No chance. He’s said so many times. He is only running for president,” he said.
In Pennsylvania, former Rep. Joe Sestak and former gubernatorial chief of staff Kathleen McGinty are squaring off in a toss-up Democratic primary.
Incumbent GOP Sen. Pat Toomey (Pa.) has avoided controversy and moved to the middle on gun control by teaming up with centrist Democratic Sen. Joe Manchin (W.Va.) on legislation to expand background checks.
Clinton led Bush by 8 percentage points and Trump by 13 in Pennsylvania, according to a late-August poll by Quinnipiac.
Jennifer Duffy, a handicapper and senior editor of the Cook Political Report, said the presidential race would largely determine the fates of Sens. Rob Portman (R) and Kelly Ayotte (R) in Ohio and New Hampshire, respectively.
“Ayotte and Portman could do everything right. They could run the better campaign, but in a presidential race, if the state goes Democrat, it may not matter,” she said.
In New Hampshire, Clinton leads Bush by 8 points, Trump by 2 points, Rubio by 8 points and businesswoman Carly Fiorina by 2 points.
Strategists and handicappers say the Democrats’ chances of knocking off Ayotte also depends on whether Gov. Maggie Hassan, their top recruit, jumps in the race.
In Ohio, former Gov. Ted Strickland led Portman by 3 points in a recent Quinnipiac poll, though he has raised less money.
The third tier of potential Democratic targets includes North Carolina and Indiana, which both lean Republican but voted for Obama in 2008.
The two Republican pick-up opportunities, Nevada and Colorado, are also presidential battlegrounds. In those states, the national debate on immigration — which Trump has dominated by calling for construction of a 2,000-mile wall along the Mexican border — could affect the outcome.
Hispanics made up 14 percent of eligible voters in Colorado and 16 percent in Nevada in 2014.
Republicans say Sen. Michael Bennet (D-Colo.) is the most vulnerable Senate incumbent in the nation and note his approval numbers are worse than recently ousted former Sen. Mark Udall’s (D-Colo.) were at a similar point last cycle.
But the GOP has yet to recruit a candidate as promising as freshman Sen. Cory Gardner, who beat Udall.
— This story was updated at 9:49 a.m.