Forget the swing voters. The voters who will determine control of the Senate this year are anything but. Instead, they are voters who are already firmly in President Obama's or Mitt Romney's camp but who are open to voting for the opposite party in the Senate race.
As Americans increasingly vote in parliamentary patterns, in which the vast majority of partisans stick to a straight-ticket ballot, the number of ticket-splitters either party can court is shrinking. And yet they remain crucial as both parties desperately seek to build coalitions that can get them to 51 Senate seats.
In some states, the hunt for ticket-splitting voters is more urgent than in others. To win reelection, Republican Sen. Scott Brown of Massachusetts must convince as many as 1 in 6 Obama voters to cross party lines to keep his job. Democrat Heidi Heitkamp, who is running neck and neck with Republican Rep. Rick Berg forNorth Dakota's open Senate seat, will need to convince an equal number of Romney voters to cross over on her behalf.
But one convenient aspect of this year's competitive elections is the extent to which presidential battleground states and nail-biter Senate races dovetail. In states like Virginia, Nevada, and Wisconsin, neither presidential candidate will win a blowout victory, and neither party's Senate nominee is likely to win by more than a few percentage points. That makes the hunt for crossover voters crucial to control of the Senate.
Every race has its intricacies. Polling data compiled for both parties, for outside groups, and by independent surveys shed light on the kinds of voters who will tip the election in each state.
Former Democratic Gov. Tim Kaine sees an opportunity to attract two handfuls of Romney voters in Virginia. Women in the Richmond suburbs who fondly recall Kaine's time as governor appear marginally more likely to choose him than Obama. And men in the Northern Virginia suburbs, voters who care about transportation issues as much as anything else, might be inclined to register their disapproval of Obama -- especially with the pending budget sequester threatening defense industry jobs -- but also to stick with Kaine. In both cases, these Romney voters will likely view the Senate contest as a matchup between two well-known political figures in the Commonwealth, Kaine and Republican former Sen. George Allen, rather than between two candidates defined only by party labels. Romney, Democrats believe, has a wider appeal than does Allen.
Polling shows that voters choosing Romney and Kaine are disproportionately representative of a younger generation. More than 6 in 10 ticket-splitters are under 50 years old, while the electorate as a whole is split evenly between those over and under 50. Most ticket-splitters are self-identified independents, with whom Kaine outperforms Obama.
In Nevada, GOP Sen. Dean Heller has done an admirable job cutting into the base that Democratic Rep.Shelley Berkley needs to build. Private polling shows that more than 6 in 10 voters who say they will vote for Obama and Heller are women, while a disproportionate number are Hispanic and younger.
Public polling backs up at least some of those private numbers. A Latino Decisions/America's Voice poll conducted Sept. 22 to 28 shows Obama attracting 78 percent of Hispanics, while just 58 percent said they would back Berkley. Heller outperforms Romney by 9 points in that survey of 400 registered Latino voters.
Former Surgeon General Richard Carmona, a Democrat running for retiring Sen. Jon Kyl's seat in Arizona, is polling neck and neck with Republican Rep. Jeff Flake in a state that hasn't elected a Democratic senator since Dennis DeConcini won reelection in 1988. Carmona is competitive because a disproportionate number of women, Republican, and older Romney voters are backing him.
Private polling indicates that more than three-quarters of ticket-splitting voters here are over age 50, a group that makes up 59 percent of the electorate as a whole. And 42 percent of the small sample of crossovers are Republicans, versus about 3 in 10 of the electorate at large.
Massachusetts' Brown has been perhaps the most aggressive at targeting ticket-splitters. He will need it: Polls show Obama's support there hovering between the mid-50s and the low-60s, meaning Brown will have to convince a large number of Obama voters to back him over Democrat Elizabeth Warren.
Brown's campaign knows who these voters are. It's no accident that he located his campaign headquarters in South Boston, or that he has frequently made a point to mention union workers during televised debates. Those blue-collar Democrats who might not relate to Warren's career at Harvard are the key to Brown's chances.
Any candidate banking on crossover voters to win in November faces long odds. Since 1992, 173 Senate contests have been decided on the same day as a presidential election. Just 22 Senate winners who shared a party with the winning president won a state their presidential nominee lost. Most of those incumbents --Max Baucus in Montana, Tim Johnson in South Dakota, and Arlen Specter in Pennsylvania, to name a few -- were long-established brands of their own.
For a first-time candidate, winning over an electorate that's voting for the other party on the presidential level is a heavy lift. If just a handful of candidates can achieve that this year, they may determine which side controls the Senate in the next Congress.