The conservative super-PAC Club for Growth Action raised nearly $391,800 during the month of December, according to new filings with the Federal Election Commission.

It was the super-PAC’s largest haul since September, and it mostly stemmed from known Tea Party donor Richard Uihlein, who wrote a $250,000 check to the sister organization of the powerful anti-tax group. Uihlein is the chief executive of Uline, a packing supply company.

Donations to the super-PAC suffered from peaks and valleys in 2013 during a non-election year, ranging from just more than $2,000 in March to $683,770 in September. But the super-PAC ended the year with $1.7 million in the bank.

In one of the group’s first declarations of the year, Club for Growth’s super-PAC recently ran an advertisement targeting Rep. Justin AmashJustin AmashHouse votes to crack down on undocumented immigrants with gang ties GOP lawmaker taunts House conservatives: Trump’s base is not ‘small faction of obstructionists’ Overnight Finance: GOP plans to unveil tax framework in late September | Critical stretch for Trump tax team | Equifax CEO called to testify | Sanders unveils single-payer bill MORE’s (R-Mich.) Republican primary challenger, businessman Brian Ellis. 

Club for Growth Action only spent $150 in independent expenditures during December for “website maintenance,” according to forms.