Since the Presidential and Congressional elections are held on even years, the odd year elections like 2015 are primarily for state level politicians, such as state governor and legislature seats. While the odd year elections have relatively smaller turnout and press coverage than the even year elections, the odd year elections are still very important that affects millions of Americans across the nation. Since the deadlocks and checks and balances in Congress and the White House make it almost impossible to get anything accomplished at the federal level, it is far more realistic to look to the state and local levels to get anything done.
In short summary, the Republicans solidly won the 2015 elections
. Not a thorough domination like 2014, but a solid win for the Republicans. State governor seats for Kentucky, Louisiana, and Mississippi were up for election in 2015. Republican incumbents in Louisiana and Mississippi easily won re-election.
The Kentucky governor seat was the hot seat every analyst was watching. Democrat Governor Steve Beshear was elected back in 2007 in Kentucky, a solidly Republican state. Steve Beshear reach his second term limit in 2015, so two new candidates were running for the Kentucky governor's seat. They were vast opposites, Democrat Jack Conway would continue Gov. Beshear's liberal policies, while Republican Matt Bevin was opposed to Obamacare and promised to take down Kentucky's state version of Obamacare if elected. Polls throughout the campaign showed a tossup and close call, but the final election day results showed Republican Matt Bevin solidly won 53% to 44%.
In purple swing state Virginia, Democrats invested heavily to win the majority of the Virginia state senate, but failed to do so. Democrats could not win state legislature seats to any significant degree. This is after the Democrats lost so many state legislatures across the nation since Obama came into power in 2009.
This wiki chart
(Historical party strength) shows Democratic control of state governors and legislatures are at an all time low in many decades, with the decline starting around 2010.
In other election results around the nation, Houston TX voters had a referendum vote to secure non-discrimination protections for gay and transgender people. It failed by a 2-to-1 margin. In a rare bright light for the Democrats in 2015, Democrats won all three open seats up for election on the Pennsylvania Supreme Court.
While the Democrats have a small lead at the federal level with the President's seat, we have to look at the whole picture, which includes the state governor seats and legislatures. The state level is even more important than the federal level, because that is where Americans can realistically expect to get any legislation done, not with the deadlocks in Congress and the White House. So looking at the whole picture at the federal and state levels, the Republicans have a small lead.