Before you step into the voting booth, make sure you have researched the downballot races. Not just races for the House and Senate, even the races way on the bottom of the ballot are important.
These races at the bottom of the ballot are often "starter" offices. School board is a favorite starter office for the wingnuts. Even in liberal areas, if people aren't paying attention, wingnuts can get on the school board, and not only can they use that as a springboard to higher office, we don't need wingnuts undermining schools. Stop the wingnuts from getting on the school board, and we may be able to keep them from higher office.
The less people pay attention to a race, the easier it is for a stealth candidate to win. The library board and park board may seem like unimportant positions, but our libraries and parks are too important to leave to people who would undermine them.
Please, take the time to examine all of the candidates for all of the offices. It really does matter.