Red-state challenge

The battle for the House has dominated discussions about the fall midterm elections. But, as the debate over the nomination of Brett Kavanaugh to the Supreme Court shows, control of the Senate could matter more to the country’s direction. The polls paint a very mixed picture as to which party will enjoy Senate control next year.

Republicans are favored to gain some Senate seats because Democrats hold most of the seats up for election. Moreover, President Donald Trump carried 10 states that Democrats currently represent, compared with only one Republican-held seat that Hillary Clinton won. The sheer weight of numbers points to some Republican gains even if the national mood tilts decidedly toward Democrats.

The polls so far, however, paint a much more nuanced view. Democratic candidates currently lead in the one Clinton-carried state, Nevada, and in two Trump-carried states, Arizona and Tennessee. Seven of those 10 endangered Democratic incumbents also lead in the polls, and in no state does any Democratic incumbent trail by an insurmountable margin.

There’s reason, though, to think these polls are high-water marks for Democrats. In 2014, six Democratic incumbents led their GOP challengers based on the average of all polls taken in July. Five of those six lost in November. In 2012, Republican incumbents or other candidates in nine contested seats either led or were within 1 point in July. They won only two of those nine seats on Election Day.

Indeed, only Nevada’s Jacky Rosen is a near lock to flip a GOP-held state. Incumbent Dean Heller is receiving around 40 to 41 percent in the most recent polls, and only one previously elected incumbent since 2006—Pat Roberts of Kansas—has won after polling so low in July.

These data show two things: Campaigns matter, and so do a state’s demographics. Current Democratic incumbents Claire McCaskill and Joe Donnelly won their races in 2012 after their Republican opponents self-destructed from ill-considered comments about rape and abortion. More tellingly, however, most of the other races where early leads faded involved an incumbent or former governor running against a candidate who was not as well-known. As the races heated up and more voters learned about the challenger, that person rose in the polls, presumably on the backs of consolidating support among voters likely to support a candidate from that party.

Thus, in 2012 Elizabeth Warren came from behind to best GOP incumbent Scott Brown in Democratic Massachusetts, while in 2014 numerous Republicans came from behind in heavily red states like Alaska and Louisiana or purple states like Colorado and North Carolina.

That latter factor works heavily in the GOP’s favor this fall. Tennessee, for example, went for Trump by 26 points. Former Gov. Phil Bredesen leads the GOP’s likely nominee, U.S. Rep. Marsha Blackburn, by an average of 5 points so far, but she has never run a race in the GOP’s heartland of eastern Tennessee. Once she starts to advertise there, Bredesen’s built-in advantage from being a well-known state figure will fade. He might still win, but the race is highly likely to tighten before the end.

Very few Democratic incumbents in Trump-carried states should feel safe despite the early poll advantages. Since 2006, only incumbents who consistently receive at or near 50 percent in July head-to-head matchups have won the vast majority of their races. So far that is good news only for West Virginia’s Joe Manchin and Ohio’s Sherrod Brown, each of whom has received over 50 percent in every public poll since May. The other Democratic incumbents will have to fight hard against the pull of their states’ Republican tendencies.

Elections should never be called this far from Election Day, but the data show that Republicans are likely to retain Senate control.