2010. It also gave them the chance to draw very favourable maps for the next 10 years.
This is pretty much the answer, but I think republicans overall are trusted a little better at the local level.
I think it's more that people who self-identify as Republicans are more "loyal" to their party than people who self-identify as Democrats.
There are Republicans in places like Vermont and New York who will dutifully tick off all the R boxes up and down the ticket even if they quietly murmur that some of them may be a tad too conservative. There are so-called "Democrats" in Oklahoma and Kentucky who will vote in primaries like clockwork but refuse to vote for any Democrats at any level in general elections because they "lost their way" or "ain't the party of the workin' man no more."
Yes, but there are also many republicans in New England who voted for Obama. You can argue republicans are
more loyal, but New England at the state level certainly proves there are many republicans who vote for democrats at the federal level because the party became too far right. Each region of the country will always have voters that will vote straight ticket republican and democrat, and each region of the country has those voters who vote opposite of their own local party.