A former Iowa state senator is beginning his prison sentence for his part in an endorsement bribery scandal in the 2012 Iowa caucuses.

Kent Sorenson began a 15-month prison sentence as a result of accepting $73,000 to switch his endorsement from then-Rep. Michele Bachmann to then-Rep. Ron Paul in the days before the caucuses, the Des Moines Register reported.

Sorenson, who was at the time a rising tea party star, was forced to resign his Senate seat after a special prosecutor’s report found he also received payments for his endorsement of Bachmann.

Sorenson is still appealing the sentence handed down from Senior U.S. District Judge Robert Pratt in January. Sorenson had to self-surrender on Tuesday after Pratt denied a request to reschedule the self-surrender date to April to complete his taxes and “wrap up pending financial matters.”

A blog post supposedly written by Sorenson called Pratt “politically-motivated.”

“I have been very open about the mistakes I have made,” the post read, according to the Register. “I truly believe the sentence I received was unjust.”

Three Paul operatives, including Jesse Benton, a former campaign manager for Senate Majority Leader Mitch McConnell, were convicted of a variety of charges. Benton was sentenced to two years of probation.