The same dynamic that powered the Democrats’ unexpected Senate gains this fall could also give the party more leverage to drive its legislative agenda through the chamber in the months ahead.
At the core of the Democrats’ surprising pickup of two Senate seats was a consistent pattern. In almost every major contested Senate race, exit polls showed that the Democratic candidate won more support among voters who also backed President Obama than the Republican nominee did among voters who backed Mitt Romney.
In two sides of the same coin, that means almost all major Democratic Senate candidates did a better job than their Republican rivals of unifying their base and attracting more crossover voters. That pattern allowed Democrats to virtually sweep the Senate races in the states Obama that won and to triumph in four states that Romney carried decisively—Indiana, Missouri, Montana, and North Dakota.
This electoral dynamic could have important legislative implications. Every Democratic Senate winner, even those in states that Obama lost, was sent to Washington behind commanding majorities from the voters who also supported the president. That could increase their incentive to stand with him on the biggest legislative fights. “Even [for] Democrats in purple or red states,” says Democratic strategist Jim Jordan, who helped lead an independent expenditure campaign for the party’s congressional candidates, the results should induce “a little less hesitation to sign onto Obama’s agenda.”
Notwithstanding the four Democratic red-state triumphs, this election mostly confirmed the rise since the 1970s of parliamentary-style party-line voting between presidential and Senate races. With only three exceptions (all for Republican candidates), at least 80 percent of Obama and Romney voters also backed their party’s Senate candidate in each of the 14 top races for which exit polls are available.
Within that broad overall trajectory, though, Democrats benefited from extraordinary levels of unity. All but three of those 14 Democratic Senate candidates won support from at least 92 percent of Obama voters. That’s well beyond even the level of party unity evident in 2004 when George W. Bush won reelection.
Republicans this year consistently suffered slightly greater defections. The Democratic Senate candidate inspired more ticket-splitting among Romney voters than the Republican did among Obama voters in every race except four: Connecticut and Massachusetts (where Democratic candidates Chris Murphy and Elizabeth Warren still won handily behind Obama’s comfortable margins) and Nevada, where Democratic nominee Shelley Berkley lost amid ethics questions. (In Wisconsin, Democrat Tammy Baldwin and Republican Tommy Thompson inspired equal crossover, but that allowed her to win because of Obama’s victory in the state.)
This imbalance was particularly pronounced in the Democratic red-state victories. In Missouri, reelected Democratic Sen. Claire McCaskill won 20 percent of Romney voters but lost only 1 percent of Obama supporters. In Democrat Joe Donnelly’s winning Indiana campaign, he captured 15 percent of Romney voters but surrendered only 3 percent of Obama’s.