If Republicans pick him, they will show that they've learned nothing - and that they no longer have any truly safe Senate seats.
Fifth, will there be a "wave" in which most of the competitive races break to one party or the other? Republicans are placing their hopes in the dubious theory that the public gets a "six-year itch" during a two-term presidency.
It may also be that Republicans now have a strong advantage in midterm elections, in which a lot fewer Americans vote than presidential elections.
If the Democrats can bring their edge in turning out voters from 2012 to the midterms, on the other hand, we could see a wave for them.
Sixth - the big one - will control of the Senate flip to the Republicans?
The map favors them: Twenty-one Democratic seats will be up for election in 2014, compared with 14 Republican ones, and Republicans need a net gain of only six to get a majority.
But the map favored Republicans in 2006 and 2012, too, and they managed to lose ground both times.
Republicans are well positioned to win seats from Democrats who are retiring in West Virginia, South Dakota and Montana. But they aren't running heavyweight candidates in Iowa or Michigan, where Democratic retirements have also created opportunities.
It's true that Republicans haven't won a Senate seat in Michigan since 1994, but they did very well there in the last midterm elections - picking up the governorship and both houses of the state legislature.
Republicans also have no strong candidate yet in Minnesota, where Sen. Al Franken is nearing the end of a first term he barely won in the 2008 Democratic landslide.
Alaska Democrat Mark Begich, another bare winner in 2008, doesn't have a challenger worth sweating over yet, either.
Based on the way the races look now, then, a Republican takeover of the Senate is unlikely.
Too much would have to go just right for it to happen. But that assessment is subject to revision - especially if Obamacare stays unpopular and the Republicans get their act together.
Ponnuru is a Bloomberg View columnist, a visiting fellow at the American Enterprise Institute and a senior editor at the National Review. This column first appeared in the Washington Post.