Democrats have won 6 GOP-held seats in 2017. Republicans have won 0 Democratic seats.

The 2016 election map.

Washington (CNN)On Tuesday night, Democrats flipped two Republican-held state legislative seats -- one in Oklahoma, one in New Hampshire -- that Donald Trump carried in the 2016 election.

That makes six turnovers from Republican to Democrat in contested state House and Senate races so far in 2017 -- and 26 out of 35 races (at the state legislative and congressional level) in which the Democratic nominee has overperformed Hillary Clinton's showing last November. (Worth noting: Republicans have yet to flip a Democratic-controlled seat so far this year.)
Republicans will, rightly, note that in each of the contested special elections for US Congress, Democrats may have improved on Clinton's performance but they weren't able to actually win. Close doesn't count in politics.
Which is true! As is the fact that Republicans picked up a massive amount of state legislative seats in the Obama era -- well over 900 -- and were bound to give some of them back eventually. And that each race, of course, is unique -- and not necessarily indicative of any broader national trend.
    But, we also know from the history of congressional wave elections that there do tend to be canaries in the coal mines -- a race or a set of races that reveal that something is happening out in the country that we need to pay attention to. And the numbers I cited above suggest that something just might be happening.
    Let's look at the two races on Tuesday night.
    In New Hampshire, a Democrat named Charlie St. Clair won a special election by 12 points for the seat vacated by Republican Robert Fisher. Fisher became a national news story when it was revealed that he had founded the controversial "Red Pill" forum on Reddit and had expressed a number of misogynistic views in that space. While Fisher's implosion undoubtedly impacted the GOP brand in the district, it is still somewhat remarkable that St. Clair won a seat so convincingly that Trump carried by 17 points in November 2016. (And a seat where Republicans had a 12-point registration advantage.)
    In Oklahoma, Democrat Jacob Rosecrants scored a 20-point victory in a Norman-based seat that had been held by Republican Scott Martin, who resigned to become the head of the local Chamber of Commerce. Rosecrants had essentially been running for the seat for the last two years, having lost to Martin by 20 points last fall. In that 2016 general election, Trump carried the district by 11 points, however.
    As the Oklahoman newspaper notes, Rosecrants' win is the third Democratic pickup of a Republican-held state legislative seat already this year. (Don't get too excited, Democrats. With Rosecrants' victory, Democrats now control just 28 of the 100 seats in the Oklahoma state House.)
    Tuesday's results come hard on the heels of a trio of retirements in the past week from Republican members of Congress who represent swing seats. Of the 23 members who represent districts that Clinton carried in 2016, two are already heading for the exits in 2018: Reps. Ileana Ros-Lehtinen (Florida) and Dave Reichert (Washington). Several others -- like Dave Trott in Michigan -- are leaving seats where Trump won by less-than-convincing margins.
    And, as The New York Times' Nate Cohn noted -- citing Daniel Donner's data -- Wednesday morning on Twitter, the number of Republican open seats is running far ahead of where it's been in election cycles of the recent past.
    It's no secret that open seats are far more likely to flip party control than when an incumbent runs. Which is why Republicans are doing all they can right now to convince wavering members to stick around for another term.
    But, combine Trump's unpopularity, historic midterm patterns for the president's party and the early-warning signs in state legislative seat and that is looking like a tougher and tougher sell.
    CORRECTION: An earlier version of this story misspelled Dave Trott's name.