Noteworthy: Since 1976, every presidential year in which Wisconsin also had a U.S. Senate race ended up carrying for the same party at both levels. So, incumbent Republican U.S. Sen. Ron Johnson better hope for a Republican pickup of the White House and the state of Wisconsin at the presidential level come 2016.
Here is the pattern (covering, in fact, the last 10 presidential election cycles):
1976
President: Jimmy Carter, Democratic pickup (and unseated incumbent Republican president Gerald Ford)
Senate: William Proxmire, incumbent Democrat
1980
President: Ronald Reagan, Republican pickup (unseated incumbent Democratic president Jimmy Carter)
Senate: Bob Kasten, Republican pickup (unseated incumbent Democratic U.S. Sen. Gaylord Nelson)
1984
President: Ronald Reagan, Republican hold (re-elected)
Senate: no scheduled race
1988
President: Michael Dukakis, Democratic pickup
Senate: Herb Kohl, Democratic hold (won open seat that was being vacated, due to retirement, of incumbent Democratic U.S. Sen. William Proxmire)
1992
President: Bill Clinton, Democratic hold (unseated incumbent Republican president George Bush)
Senate: Russ Feingold, Democratic pickup (unseated incumbent Republican U.S. Sen. Bob Kasten)
1996
President: Bill Clinton, Democratic hold (re-elected)
Senate: no scheduled race
2000
President: Al Gore, Democratic hold (in a non-incumbent election year in which his incumbent party lost the White House)
Senate: Herb Kohl, Democratic hold (re-elected)
2004
President: John Kerry, Democratic hold
Senate: Russ Feingold, Democratic hold (re-elected)
2008
President: Barack Obama, Democratic hold (won presidency, in non-incumbent year, and flipped the White House party from 2004 Republican to 2008 Democratic)
Senate: no scheduled race
2012
President: Barack Obama, Democratic hold (re-elected)
Senate: Tammy Baldwin, Democratic hold (won open race of seat that was being vacated, due to retirement, of incumbent Democratic U.S. Sen. Herb Kohl)