The GOP looks like it can maintain its majority in the Senate, but the main Senate super PAC has decided to spend $21 million more in six races just to be on the safe side. The Senate Leadership Fund has moved its concentration to New Hampshire, North Carolina, Indiana, Missouri, Nevada, and Pennsylvania.

Republicans have become more confident since they have seen voters separate GOP presidential candidate Donald Trump from the Senate candidates. This week, The New York Times Upshot blog said the GOP had a 53% of maintaining the majority. That same blog gave the GOP only a 40% chance in August.

Steven Law, the PAC’s president, acknowledged these quick changes, explaining that it hurts the Democrats because “their shift to the majority is shifting to states that Mitt Romney won.” The PAC even pulled back ads in Ohio since Sen. Rob Portman’s lead over former Governor Ted Strickland has widened.

Plus, the super PAC has received more money from major donors due to the optimism that the GOP will win the seats:

Altogether, the Senate Leadership Fund plans to spend $76 million in September and October — and the total could swell larger by Election Day, thanks to mega-donors such as Miriam and Sheldon Adelson, who gave the super PAC $20 million in August. The spending blitz comes after an allied nonprofit group, One Nation, shelled out $26 million on “issue ads” touting GOP candidates between last October and August. That organization is not required to disclose its contributors.

Law said donors have flocked to protect the Senate majority because they see the fight as a “concrete, achievable goal” — and one in which outside spending can have a clear impact, unlike in the White House race, which is “much larger, more chaotic and harder to predict.”

The Senate Leadership Fund has invested the most money into Sen. Kelly Ayotte’s campaign in New Hampshire mainly because many outside groups have not funded her campaign. Her opponent Maggie Hassan has received money and support from labor unions and the Democratic Senate Majority Pac:

“The terrain is tough and Maggie Hassan is probably one of the Democrats’ better recruits, but overall we think Ayotte has run a very good race,” he said. “We actually feel like the dynamics in that race are starting to improve in our favor, but the one glaring consideration we had was the weight of message disparity.”

It remains a nail biter, though. A poll from Democratic PAC End Citizens United shows Hassan with a slight lead. However, other polls show Ayotte has the edge over Hassan.

The PAC has also concentrated on Indiana where former senator Evan Bayh wants to gain back the seat he gave up. Law said the group has increased the support to Rep. Todd Young’s campaign by $4.5 million:

“We think Indiana is going to be the Democrats’ Waterloo,” Law said. “They are going to spend a fortune here, and they are going to lose.”

Law might be onto something there. Bayh has enjoyed a lead over Young, but recent polls have shown Bayh’s slowly losing his grip:

Bayh, who strategists say still has the upper hand, went from a double-digit lead in August to a 4-point edge, within the margin of error in a WTHR/Howey Politics poll, earlier this month.

“Anyone who thought this was going to be a cakewalk for [Bayh] I think was making a mistake,” said Andrew Downs, a political science professor at Indiana University-Purdue University Fort Wayne. “He had not run a campaign in 12 years, and the nature of campaigning has changed.”