In Lower Saxony, polls show the FDP short of the 5% support needed to stay in the state legislature, which endangers popular conservative governor David McAllister's chances of keeping his job.
However, Merkel said she is "very optimistic that the (Free Democrats) will, on their own strength, with their ideas and their share in the success of the work of both the Lower Saxony state government and the federal government, be able to convince people."
The Lower Saxony election follows a rough start for Merkel's center-left challenger in the national elections, former Finance Minister Peer Steinbrueck.
He drew criticism this week for saying the chancellor earns too little and that Merkel has an advantage because she's a woman -- adding to earlier controversy over his high earnings from public speaking. Merkel coolly dismissed a question about her challenger's performance."To be honest, I take care of my own performance and I'm very satisfied with that," she said. "The rest is for others to comment on."