Bundestag parliament chief Norbert Lammert warned an increasing German trend toward not voting could have unforeseeable consequences, Der Spiegel reported.
"It's not as if non-voting had no influence," Lammert said in comments cited by the German news website. "It has an influence -- though but usually not the intended one."
Analysts said the chancellor would likely scrape through the parliamentary election and retain office but faced potential losses because of public anger over her perceived inaction in a growing controversy over spying on individuals.
Much of the public outrage is directed at Britain and the United States. In neighboring Belgium, politicians are debating ways of retaliating against U.K. spy agencies and German sentiment against both the United States and Britain is less restrained than before.
Merkel's re-election seems assured but her majority in Bundestag seems less certain, and is increasingly seen as likely to suffer because of the dual issues -- the spying scandal and an increasingly popular German view that not voting is "cool."
"A growing share of younger people in Germany are opting not to vote. A favorite non-voter adage is that you are more likely to be killed by a speeding car on your way to the polling station than to influence politics by casting your vote," Der Spiegel said.
A poll Thursday gave Merkel's conservative Christian Democrats and her junior coalition partner Free Democrats a lead of just 1 percent over opposition parties.
"The tension is rising in Germany as the election campaign draws to a close," Der Spiegel said.
The capital has been the scene of repeated marches and protests over government surveillance of citizens.
Organizers of a "Freedom Not Fear" protest rally this month drew thousands of participants who denounced Merkel for going along with the United States and Britain sifting through databases of people's email, online chat and Internet browsing histories without prior court authorization.
Speakers called for the defeat of Merkel in Sunday's election. Analysts are agreed a major setback for Merkel would spell trouble for the European Union as a whole.
The election campaign highlighted Germany's increasingly articulate ultra-right wing which targeted parliamentary candidates with immigrant roots. A letter addressed to candidates of non-German racial background asked them to "go home instead of immigrating."
Other right-wing campaigners targeted Germany's rising Muslim politicians, with one slogan declaring "miniskirts not minarets," Deutsche Welle radio reported.