HARRISBURG, Pa. (AP) – A national super PAC that works to elect Democrats to the U.S. Senate says it’s reserved about $9 million in television advertising to help Katie McGinty beat Republican incumbent Pat Toomey.

Monday’s revelation ups the ante in a closely-watched and increasingly expensive race that could determine control of the U.S. Senate next year.

The Senate Majority PAC says the reservation begins in September and runs through the Nov. 8 election. It says it could reserve more TV ad time later.

The Senate Majority PAC says, to date, it’s already spent approximately $2 million on TV ads in Pennsylvania, and its sister organization, Majority Forward, has spent approximately $700,000.

Toomey is viewed as one of the most vulnerable Republicans up for election this year. The cost of the race is on track to exceed $50 million.