Kyle Kirkwood hangs on to win Freedom 250 Grand Prix in Washington

However, some late cautions erased much of Kirkwood's work, and presented a golden opportunity to Arrow McLaren's Christian Lundgaard.

Lundgaard - who is currently without a drive for next season - was strong early in the final green flag run thanks to his red alternate tires, an advantage over Kirkwood's primary set, but it seemed like they started to fall off as the laps wound down.

Kirkwood was followed by Lundgaard in second, while Kirkwood's Andretti Global teammate Will Power took the last step of the podium.

The win was crucial for Kirkwood's championship hopes as it cut Palou's championship lead down to 91 points.

The Spaniard had a rough day at the office. He was dealt a drive-thru penalty on his first pit stop of the race and his team had an issue with his front left tire on another stop.

Then, on lap 122, Palou made a third uncharacteristic error and crashed, bringing out a late caution.

It was Kirkwood's second win of the season. His first came at the Grand Prix of Arlington earlier this season.

The 27-year-old now has seven career wins, six of which have come on street circuits.

It remains to be seen whether Kirkwood will get a chance to go back-to-back in the nation's capital. The Freedom 250 Grand Prix is expected to be a one-off event to mark the celebration of America's 250th anniversary. 

There are three races left in the IndyCar season, meaning the championship battle is still very much on. 

Next weekend is a double-header at the Milwaukee Mile, while the season finale will take place at WeatherTech Raceway Laguna Seca on September 6.

All NTT IndyCar Series races air on FOX.