Of all the campaign issues that incumbent Republican senators face in 2016, the most vexing may be Donald Trump. As their party's presidential nominee sinks in the polls, Republican senators in battleground states must decide if they should align with him or hitch their fortunes to that rarest group of voters -- the ticket-splitters.
The most recent polling shows Democrats, who currently hold 46 seats in the Senate, are favored in to pick up seats in Illinois and Wisconsin. That means control of the U.S. Senate starting in January likely hinges on what happens in four closely contested states: New Hampshire, North Carolina, Ohio and Pennsylvania. In each state Hillary Clinton currently leads Donald Trump in polls, in some cases substantially.
That seems to leave Sen. Kelly Ayotte in New Hampshire, Sen. Richard Burr in North Carolina, Sen. Rob Portman in Ohio and Sen. Pat Toomey in Pennsylvania with one big hope for November -- they need to get a substantial number of voters not voting for Trump in the presidential race to pull the lever for them.
Despite the many eulogies for the practice and an increasingly polarized electorate, ticket-splitting is not dead in America. In 2012 there were six states where voters selected presidential and senate candidates from different parties: Indiana, Missouri, Montana, Nevada, North Dakota and West Virginia.
And two races in particular were driven by voters opting against controversial candidates. In Missouri and Indiana, Republican Mitt Romney won the presidential vote, while Democratic senate candidates, incumbent Claire McCaskill and then-Rep. Joe Donnelly, won after their GOP opponents took extreme positions or made extreme comments on rape and abortion.
In 2012, McCaskill received about 400,000 more votes than President Obama in Missouri. Donnelly received about 200,000 more votes than Obama in Indiana. Those are substantial numbers of split-ticket voters.
But there are differences between 2012 and this election cycle.
In 2012 the "splitting" did not take place at the top of the ticket. Indiana and Missouri have a strong Republican lean and voters in those states sided with the Republican candidate for president - the office that usually brings the most voters to the polls. Voters changed their vote further down the ballot.
In 2016, Ayotte, Burr, Portman and Toomey would need something else. They would need voters who don't support the Republican running for president - the office that usually brings most voters to the polls - to vote Republican further down the ballot.
That is, they'll need to give down-ballot Republican voters a reason to show up on Election Day.
And, more to the point, there is a problematic bit of math behind the ticket-splitter strategy. If the candidates push away from Trump they may anger Trump's supporters. Thus the problem, how many Trump voters do the candidates give up if they renounce the nominee and how many non-Trump or anti-Trump voters do they gain?
What's a battleground incumbent Republican to do? It will likely depend on the margin in the state and well as its demographic composition.
Toomey in Pennsylvania: Of the four key Senate races, Pat Toomey may have the hardest call to make on Trump. He still hasn't announced whether he will vote for the GOP nominee. The latest NBC News/Wall Street Journal/Marist Poll has Trump down 9 points in Pennsylvania and Toomey is down 4 points in his race against former state environmental official Katie McGinty. That would suggest that Toomey should run away from Trump.
But Pennsylvania is a complicated state full of a key Trump demographic group, whites with less than a bachelor's degree. In 2012, those voters made up 34% of the total electorate and they are crucial for Republican candidates in the state. They make up a lot of the GOP vote in the central and western parts of the state (in the western half of the state only two counties are above the national average for having at least a bachelor's degree). Meanwhile the southeastern corner around Philadelphia is better educated (four densely populated counties above the national average on college degrees) and strongly opposed to Trump.
Toomey has to be careful not to support Trump too much for fear alienating suburban Philly, but he also has to be careful not to dump Trump because of those Trump bases of support elsewhere. That's a tricky calculus and it has some media outlets calling for him to make a decision on the GOP nominee.
Burr in North Carolina: Richard Burr is also in a challenging position. He has endorsed Trump, which means he would have to actively take back that endorsement to move away from the nominee. In the latest NBC/WSJ/Marist poll Trump is down nine points to Clinton, while Burr is down two points in his race against Deborah Ross. Those numbers suggest he's weathering Trump's poll decline fairly well, but there may be other concerns lurking. At least one North Carolina media outlet recently called for Burr to reverse his support for Trump.
In the latest NBC/WSJ/Marist Poll, Burr is doing much better with white college-educated voters than Trump. Burr actually leads among those voters by two points, while Trump among them by seven. That's the number to watch in upcoming polls. If Burr's support among college-educated white voters declines, it may be a sign that his closer ties to Trump are hurting him.
Ayotte in New Hampshire: Kelly Ayotte is walking the Trump tight rope, announcing she will vote for him, but not support him. With polls showing the Republican nominee falling far behind in a state he once hoped to win, he seems to have become a drag on her.
The Real Clear Politics poll average shows Trump trails Hillary Clinton by 8.2 points in the state, while Ayotte trails her opponent Gov. Maggie Hassan by only one point. The challenge for Ayotte will likely be college-educated voters, a group that polls show is down on Trump. New Hampshire has a higher percentage of voters with a bachelor's degree or more than the national average. That's particularly true with the big vote-producing counties in the southern part of the state. The question is whether her vote-but-not-support stance be enough to appease those voters.
Portman in Ohio: Of the four senators here, Rob Portman is arguably in the best position when it comes to winning Trump ticket splitters. The senator offered a lukewarm endorsement to Trump in May, but the Ohio Republican establishment has not rallied behind the presidential nominee - Republican Gov. John Kasich still has not endorsed Trump. In other words, Portman may not have to say anything about the Republican nominee and still have the support of moderate Republicans, while having the seal of approval among Trump voters.
The latest NBC/WSJ/Marist poll shows Trump trailing by 5 points in the state, but Portman leading by 5 in his race against former Ohio Gov. Ted Strickland. That 10-point ticket-split number, combined with the Ohio GOP's attitude toward Trump, may give Portman some room to breathe unless Trump's numbers take another big dip.