The largest U.S. Senate-focused Democratic super PAC on Monday plunked down $5.2 million for fall TV advertising aimed at unseating U.S. Sen. Cory Gardner.

It’s part of the Senate Majority PAC’s ad reservations in five battleground states totaling nearly $70 million. The buys come a week after the group’s Republican counterpart, the Senate Leadership Fund, booked $67 million in six states, including a $5.5 million reservation in Colorado.

“Our offensive strategy in 2020 is paying off, as Democrats continue to expand the Senate battlefield and force Mitch McConnell and Republicans to spend everywhere, even in McConnell’s home state of Kentucky,” said J.B. Poersch, SMP’s president, in a statement.

“We are starting earlier than ever this cycle to keep the pressure on vulnerable Republican incumbents and hold them accountable for their records back home. Our massive early investment is a sign of things to come as we prepare to compete deep into the map in our bid to retake the Senate majority.”

Democrats have to flip four Senate seats currently held by Republicans in order to take the majority in the chamber, or three seats if Democrats win the presidency.

Colorado’s race is regularly rated by election forecasters as this year’s most likely Democratic pick-up. Gardner, who is seeking his second term, has trailed leading Democratic candidate John Hickenlooper, a former two-term governor, by double digits in available public polling.

Both sides’ Senate super PACs put Colorado’s ad reservations at the bottom of their battleground state spending.

The SMP reservations also include $25.6 million in North Carolina, $15.7 million in Arizona, $13.1 million in Iowa and $9.6 million in Maine – in every state but Colorado representing a higher initial buy than the GOP group’s bookings, as first reported by The Washington Post.

The Democratic group went on the air in Colorado earlier this month with a $640,000 ad campaign linking Gardner with President Donald Trump while pushing back on a an ad attacking Hickenlooper.

A spokeswoman for SMP said the PAC plans to increase reservations “on a rolling basis” and could change the battleground map as Election Day approaches. It also plans to maintain its digital ad program.

Jack Pandol, the GOP-aligned Senate Leadership Fund’s communications director, took some shots at Hickenlooper in a comment about the Democratic group’s new ad buy.

“Democrats will need every penny of their liberal donors’ money to defend John Hickenlooper’s highly questionable record,” Pandol told Colorado Politics. “This is going to be a very competitive race and we look forward to making sure Coloradans fully understand why Hickenlooper is unfit to serve them in the U.S. Senate.”