WATCH: Grimes Burns McConnell With Tough New Attack Ad

Kentucky Secretary of State Alison Lundergan Grimes (D) escalated her attacks against Senate Minority Leader Mitch McConnell (R-KY) on Monday, releasing the toughest ad of her young U.S. Senate campaign.

The ad, titled “Fire,” compares McConnell’s conduct during the government shutdown crisis to lighting a house on fire and then claiming credit for putting it out.

“He calls himself a ‘proud guardian of gridlock,'” the ad’s narrator says. “He’s blocked the Senate over 400 times. Then voted to shut down the government, hurting Kentucky’s economy.”

“Mitch McConnell can’t light the house on fire and then claim credit for putting it out,” the ad continues, “especially while it’s still burning.”

The web video reiterates a theme that Grimes’ campaign has repeated since McConnell began attempting to claim credit for ending the unpopular government shutdown. It also represents a significant escalation in what is expected to be among the most negative races in the country in 2014.

While Grimes attacks McConnell for starting the government shutdown, right-wing supporters of the minority leader’s Republican primary opponent, Matt Bevin, are attacking him for ending it. That McConnell has proudly touted his role in ending the crisis shows that he views Grimes as a far greater threat to his re-election hopes.

Early polling of the race suggests that a McConnell vs. Grimes general election match-up would begin as a toss-up.