If you canvass for a particular person or political party, you go around an area trying to persuade people to vote for that person or party.
例句
I'm canvassing for the Conservative Party...我在为保守党拉选票。
VERB
征询,征求(公众意见)
If you canvass public opinion, you find out how people feel about a particular subject.
例句
Members of Parliament are spending the weekend canvassing opinion in their constituencies.国会议员这个周末要向所在选区的选民征求意见。The poll canvassed the views of almost eighty economists.民意调查征询了将近80位经济学家的意见。