Fewer than half of Americans are very confident that their vote for president will be counted correctly — and most say their ballot will not matter anyway because the political process is so dominated by corporate interests.

These are among the results of a P.R.R.I. poll released on Tuesday showing a nation that is deeply ambivalent about the electoral process.

Americans are almost evenly divided on whether fraud or voter repression is a bigger problem, despite many studies showing that fraud is almost nonexistent nationwide.

The findings suggest there may be at least some audience for Donald J. Trump’s claims that the presidential election could be “rigged.”