Tonight is the most important game in the history of the Washington Nationals and, if Jonah Keri will forgive me here, probably the Montreal Expos, too. The Nats have never won a playoff series before, and tonight, they have a home game against the defending World Series champions that will either send them to Los Angeles for their first-ever National League Championship Series or back home, reeling again from a devastating October defeat.

As is usually the case with Washington sports teams, there is no middle ground. Tonight is either covered in glory or misery. That it comes on the heels of drama about whether or not Stephen Strasburg was well enough to pitch -- he was, as it turned out! -- is only fitting. It's always something.

Adding to the pressure is a ticking clock for the Nats. After next year, Bryce Harper is a free agent, as well as Daniel Murphy and Gio Gonzalez. The Max Scherzer-Strasburg combo is around for another four years, but Harper, the centerpiece and lifeblood of this team, could be gone after next year. You only get so many chances. You never know: This could even be the last one.

If the Nationals win tonight, all those "the ceiling is the NLCS" jokes will go away, and they'll have a party that'll make a ton of people late to work tomorrow. And they will forget all the postseason disappointments that led up to this point. Tonight will either be the start of a whole new chapter in Nationals/Expos history … or the saddest one in the ongoing set of disappointments. As we prepare for the biggest game this franchise has ever played, let's have a look back at the Nats/Expos' postseason history up to this point.

1981 League Championship Series: Dodgers beat Expos in five games

It should be noted that the Expos did, in fact, win a five-game series back in 1981. But the caveat is that '81 was a strike year that knocked out two months of the season, and rather than pick up the standings where they stood when the strike began, MLB had the first-half winner and a second-half winner play a five-game series to determine the division winners. The Expos won the NL East in the second-half -- by half a game -- and then beat the Phillies.

In the NLCS, the Expos took a 2-1 series lead over the Dodgers before getting shelled in Game 4 and heading back to Olympic Stadium for a Game 5. They took a 1-0 lead in the first inning off Fernando Valenzuela -- on an Andre Dawson double-play grounder -- but the Dodgers tied it in the fifth on a Valenzuela RBI groundout. The game remained tied until the top of the ninth, when Rick Monday, facing reliever Steve Rogers with two outs, did this:

Valenzuela stayed in for the complete game in the ninth but after getting two outs, walked Gary Carter and Larry Parrish, leading Tommy Lasorda to (at last!) go to the bullpen. Bob Welch got Jerry White to ground out, and the Expos would never play a postseason game again. This game is still known as "Blue Monday" in Montreal. It bummed me out just typing about it.

2012 National League Division Series: Cardinals beat Nationals in five games

The 2012 Nats were a special team, one that won 98 games (still a franchise record) and had two of the most electric young stars in baseball in Strasburg and Harper, the latter of which hit 22 homers despite being only 19 freaking years old. This series happened during the first year of the Wild Card Game, but the schedule hadn't been figured out entirely in time, so the Cardinals hosted the first two games of the series and the Nationals hosted the last three. Facing elimination in Game 4, the Nats had what might still be their greatest postseason memory to this point, Jayson Werth's walk-off homer in the bottom of the ninth.

This carried over to a blistering start of Game 5, with the Nationals taking a 6-0 lead. The Cardinals slowly crawled back, but they were still down 7-5 heading into the top of the ninth. Then Daniel Descalso happened, and then Pete Kozma happened, and the Nationals had their most brutal loss ever, immortalized best by Bill Barnwell's old Grantland piece, which literally ends with him and Nationals fans listening to "Everybody Hurts" in a DC bar. I feel like a jerk even bringing this game up.

2014 National League Division Series: Giants beat Nationals in four games

This one was actually a little bit less painful than all the others, if just because it was over in four rather than five. But this was also the series of the 18-inning Game 2, a postseason game that went so long that Yusmeiro Petit threw six shutout innings in relief. (Harper went 0-for-7 in that game.) This would ultimately be the Madison Bumgarner Postseason, but it's worth noting that the one game the Nats won in this series was against Bumgarner. This was also the first series where you started to wonder if Matt Williams was really the manager the Nationals wanted moving forward. (Turns out he wasn't.)

2016 National League Division Series: Dodgers beat Nationals in five games

This was another heartbreaking loss, mainly because the Nationals once again had a 2-1 series lead and couldn't close it out. They had the advantage of being at home for Game 5 during this one too, and they mounted a rally off a clearly gassed Kenley Jansen in the ninth inning. With two on, the Dodgers called for … Clayton Kershaw.

In a great tick-tock for the Los Angeles Times last year, Andy McCullough wrote about how Dodgers executives were actively shocked to see Kershaw working in the bullpen, trying to warm up for the final inning in case Jansen couldn't make it. Dave Roberts didn't want him to. The Dodgers brass didn't want him to. But he did. "Kersh is going to see if he can get loose," the trainer said. "And there was nothing we could do to stop him."

For the second time in five years, the Nationals had missed the opportunity to clinch a postseason series at home and instead watched someone else celebrate on their own field.

Tonight, it could happen for the second year in a row. Or it will be the greatest moment in Nationals history. Again: There is no middle ground.