Democrats are going after two previously unwinnable House seats in a pair of special elections starting Tuesday. It's pretty amazing that Republicans have to defend either of them.

First there was a seat in suburban Atlanta that looked competitive, and now there's a hugely Republican seat in Kansas that looks at least a little vulnerable as voters head to the polls today. The Washington Post's Dave Weigel and the New York Times's Jonathan Martin have all the details from Wichita.

It's worth emphasizing at the top that special elections are, by definition, special. They have much lower turnout and are thus more susceptible to huge upsets. And often, the wins are short-lived once the fuller electorate weighs in. Republican Scott Brown famously won a special Senate election in heavily blue Massachusetts in 2010, only to lose it two years later. And back in 2008, Democrats won conservative-leaning districts in Louisiana, Illinois and Mississippi, only to lose the first one a few months later and the other two in 2010.

But these wins can also provide a real indication of what may lie ahead in the next general election, as we found out with Brown in 2010 and the Democrats in 2008. And that's why they earn such attention and investment from the national parties. Basically, Democrats know such wins would be fleeting, but they're eager to prove President Trump is severely damaging the GOP's 2018 chances.

Even in that context, it's remarkable that Republicans are having to defend the seats in Georgia and Kansas — and especially the one in Kansas today.

To wit, in Georgia:

  • Health and Human Services Secretary Tom Prices's old 6th District went for Mitt Romney by 23 points in 2012, giving him 61 percent of the vote, according to numbers compiled by Daily Kos Elections. (Caveat: It was much closer in 2016, with Trump winning by 1.5 points, but it has historically been a very safe seat.)
  • It was the 82nd most pro-Romney district out of 234 seats that Republicans won.
  • The most pro-Romney district Democrats currently hold — Minnesota Rep. Collin C. Peterson's — gave Romney just 54 percent of the vote, seven points less than Georgia's 6th.
  • Democrats hold only two other districts that even gave Romney a majority of the vote — let alone more than 60 percent.

And in Kansas:

  • CIA Director Mike Pompeo's old district gave Romney 62 percent in 2012 and Trump 60 percent in 2016.
  • It was the 93rd most pro-Trump district in the country.
  • Only one Democratic-held district gave Trump more of its vote — again, Collin Peterson's (62 percent).
  • Democrats hold only three other districts that even gave Trump a majority.

So these are both districts that have given GOP presidential candidates 60-plus percent of the vote in recent years.

Democratic wins in either wouldn't be unprecedented. Massachusetts had just given Barack Obama 62 percent of the vote before Brown won it in 2010, and Mississippi's 1st District also gave George W. Bush 62 percent before Democrats picked it off in 2008. (The Louisiana seat went 59 percent for Bush.)

But these special elections were shocking upsets that preceded wave elections for the victorious parties. The fact that Democrats couldn't defend the bastion of liberalism that was Massachusetts in 2010 and that the GOP couldn't hold conservative districts in the Deep South in 2008 presaged very bad things for the party in power.

In Georgia and Kansas, we have some pretty similar circumstances.